Essential items to consider when getting into cycling (besides the bike!)

Welcome to road cycling, it's awesome.  I love the speed, the interaction with the city (which undoubtedly can be terrifying at times but I think overall rewarding and an important aspect of cycling prowess for a rider to be accustomed with if they want to really get into riding), the solitude, but also the companionship of riding with others.  Although if i'm honest with myself, most of my riding is done solo and becomes a great place of moving meditation.

You're hitting the ground running and buying all the right things, starting with your Dragon.  I'll be happy to offer my recommendations that come from lots of trial and error, and a willingness to open my wallet a bit, albeit smartly as the biking hobby lends itself to regular upgrading and new things (like tubeless tires) in almost endless supply.  I would consider adding the following, lengthy reasoning included:

1.  Floor pump with a gauge.  No reason to go nuts, Planet Bike makes a variety of excellent (and some crappy) bike accessories.  I've had their floor pump for at least a dozen years, and I've never had to do any maintenance to it (some pumps have you grease the inner pump tube), and it can achieve a high volume of air, up to like 150 psi or something, well beyond a rider's needs.  I have found that in 30+ years of riding (i'm 43 now) I have done more than 95% of the bike's tire pumping at my house, so a good floor pump is important.  I typically top off before each ride, and always store my bikes filled with air during the offseason to avoid tire damage, which would be slight, but can still be a thing.    

2.  CO2 Inflator and cartridges.  These came out about a dozen years ago and ended the fruitless search for an on bike mini pump that would fill my tires up fully should I need to fill them during a ride, as in fixing a flat.  A CO2 inflator and cartridge I like is the Genuine Innovations set because the inflator is really small, but any brand is fine so long as the inflator piece is small and not bulky.  The inflator is the most expensive part of the setup and can be reused indefinitely.  Replacement CO2 cartridges run about $3 and are a one and done sort of thing (make sure when buying that you match the cartridge to your inflator, i.e. threaded or threadless, there isn't a benefit to either threaded or threadless, but I've always had threaded for some reason...).  Why do I go with the CO2 setup instead of bringing a bike pump on my ride, and to that end an extra inner tube instead of the fantastically useless and cheap patch kits?  Pumping a tire from flat to rideable with a mini pump is a useless energy suck when we're already wrestling with a flat tire on the side of the road, and all but the most expensive Lezyne or Topeak pumps say that they can reach 120 or 130 psi.  My reality with both those mini pumps is that they have trouble, or rather maybe I do, reaching that 120 psi with the tiny pump.  That said, if you have a flat mid-ride, you can certainly "limp home" by pumping your tire to ~75 psi, but you'll obtain less speed and your handling will be affected with the lower tire pressure in the form of less control. 

3.  Chamois butt'r  .  Schmear a bunch of this on yourself before putting on your cycling shorts (in the same area that your short's chamois protects), and you will never ride in pain again.  I did not discover this until 2016, and I can't begin to tell you how much more comfortable I was during and after my ride.  Yes you have to put a lot of it on before the ride, but it washes off easily, doesn't stain your bike shorts, and is extremely extremely effective.  Extremely ;) 

4.  Inner tube.  As I mentioned before, patch kits don't work, and new inner tubes are like $5.  Sure they take up a bit more room in your small on-bike repair kit, but once installed, you don't have to worry about the patch falling off, or the patch constricting the inner tube once fully inflated.  Quick note with inner tubes they come with two different valves; presta or schrader.  When you were young riding that old mountain bike, it most likely had the schrader valve, which is the same type of valve you have on your car.  The schrader valve is wide, and the needle that releases the pressure is embedded in the valve.  The presta valve on the other hand is narrow and the needle is on the external part of the valve, with a little knob attached to it that we turn to lock and unlock.  The presta valve is more delicate than the schrader valve, and during your biking career you will undoubtedly break a valve while installing an inner tube (that's why we don't spend more than $5 on an inner tube) but it makes controlling the amount of air in your tire much easier.  The downside of the presta valve is that if you've run out of CO2 cartridges, lost your pump, and need to stop by a gas station to pump up, their air inflators are only compatible with Schrader...Enter the adapter:

5. Presta valve schrader adapter.  This little $4 adapter takes care of the above mentioned problem, and is an easy fix to the above issue should you ever need to stop in a gas station for some air.  Realistically, all road bikes, and most mountain bikes use the presta valve, so this adaptor is a great thing to have. 

6. Tire levers.  For changing your tire or replacing your inner tube I like the Pedro's Milk levers.  These broader levers don't break, don't scratch the wheels, and are cheap.  The thinner tire levers will break, and the little hook on the opposite end of the lever part that attaches to a spoke is rarely used.  The older Pedro Milk levers didn't have the spoke hook, so I guess they caved and added them on to these new ones, but that hasn't changed their performance. I have a pair I leave at home, and a pair I bring with me in my on-bike kit.   I also have a few other pairs laying around my house in various desks.  A quick aside, here's a great video for changing tires.  *For all things bike maintenance related, search for "Park Tools xxxxx".  For instance, if you want to adjust your rear derailleur, search for Park Tools Rear Derailleur, or something like that.  Park Tools has an extensive video library of very clear, concise, and helpful videos to aid in bike maintenance, all hosted by a pleasant giant of a man called Calvin.

7.  $5 bill.  Put this in your bike kit and forget about it.  It's great should you ever need to stop for a chocolate milk or gatorade and have forgotten your money, but more so a dollar bill, or any denomination, can be used in a pinch if you have a sidewall blowout on one of your tires.  In the case of a sidewall blowout, we would simply install a new inner tube like regular, but prior to pumping up the tire, fold the bill and put it inside of the tire to cover the blowout area, than inflate the tire.  The bill will hold the air just fine and allow you to get home.

8.  Under seat bike bag.  Carry your essentials in this bag; tire levers, inner tube, CO2 cartridge and inflator, money/cc, gummy bears or energy gel.  I like to go light with my on-bike stuff because any extra weight tacked on to the bike affects its handling as we move the bike side to side often as we ride.  That said, some people carry much more and do just fine with it.  For me, I ditched the bag altogether a few years ago and put my phone along with the above items in a ziploc bag, and put that bag in my bike jersey's back pocket.  Which brings me to the...

9.  Bike Jersey.  Many brands sizes colors and graphics are available.  The world is yours with whatever direction you want to go.  I really like the Castelli brand, and Le Coq Sportif brand, but I'm a bit of a Euro nerd...Regardless of brand, you'll want to find one that's comfortable, has two or three back pockets, and is zippered on the front to allow for ventilation when you need it. 

10. Under bike jersey/baselayer.  I might be getting a little ahead of myself, but I wish someone had told me about the baselayer years ago.  Beneath the bike jersey there are a variety of tank tops or undershirts that can be paired with your jersey depending on the outside temperature, and they go a long way to increasing your level of comfort.  When the temps dip and the winds begin to blow, this long sleeve undershirt from Castelli is made with a wind-resistant layer on the chest that cuts down significantly on the wind chill as you ride.  On the other end of the thermometer when the temps soar, a very lightweight undershirt like this Castelli baselayer helps to wick away sweat and reduces irritation and friction on your chest and stomach that can come from rubbing against a sweaty jersey for hours on end.  

11. Bib shorts.  I rode in bike shorts for years, and never found comfort until I converted to bib shorts.  The bib extends the waist of the shorts above your belly button, with straps that go over your shoulders.  This makes for a much more comfortable setup as a bicyclist is typically bent over, flexing at our waist, which causes the waistband on typical shorts to bunch up, regardless of how thin or heavy a person is.  Bib shorts remove the waistband all together, and for us larger fellows, sucks in our gut like a comfortable corset.  There are many brands of cycling bib shorts, and I've had the chance to try pearl izumi, rei's, etc etc. but I finally landed on the Castelli brand.  Bib shorts run the gamut when it comes to price, but typically the more expensive bib shorts have better hemming in the chamois, creating less friction and irritation since you'll be in the shorts for hours on end.  Regardless of the brand you go with, I would buy them in person where you can examine them, or from an online place like the above that allows for returns.  And keep in mind, you will have the bib shorts for years, so the extra money you spend now translates into a longer lasting product, not to mention much more comfort.  As a general rule, European brands tend to fit a bit longer lankier frame, like Castelli, while Pearl Izumi, an American brand, fits the more familiar American shape.  That said, I'm a husky guy and I love the Italian Castelli brand product and it fits me fine; do note, they're opening price point (read cheaper stuff) is not good.  The seams don't hold, and oh my gosh the chaffing.  But Castelli's, and to the end, Pearl Izumi's more expensive stuff is very comfortable.  

12. Hex wrench.  The most indispensable tool in your arsenal.  Over the years I've acquired far too many tools, including far too many torque wrenches and other "uni-tasking" tools, but the hex wrench from Park Tools does the crux of the work on the bike.  The hex wrench with its three sizes of wrench 4mm, 5mm, and 6mm, covers over 90% of the bolts on a bike. Park Tools make the best tools available, and you'll see their familiar blue handles in every bike shop across the US.  As far as a torque wrench goes, they are expensive, important, but really expensive.  The only components on a bike that we might deal with semi-regularly and require the exactness of a torque wrench are the bar stem and seat rail adjustment bolt, because both of these components deal with a lot of force directly exerted onto them by the rider.  Instead of spending $50 on a pricey torque wrench that only covers a couple sizes of bolt and lacks torque adjustability, this would be the rare time that I part from Park Tools selection and go with the Ritchey torque wrench.  This torque wrench does not have an adjustable newton meter (nm) rating, however at 4nm it is compatible with your bar stem, seat rail adjustment bolt, brake calipers, seat post collar, and brake lever adjuster bolts.  Beyond that, the 'two-fingers tight' method is a very good gauge of how tight you'll want to tighten any bolt on your bike.  Basically, I use the Hex wrench from above, and tighten the bolt I'm working on until I'm only able to tighten it using my pointer and middle fingers.  Two fingers tight.  Over tightening a bolt on a bike, with very few exceptions (like the crank arms that connect to your pedals) does not ensure greater safety from things falling off, quite the opposite actually.  Putting on or taking off anything on a bike, pedals, seat, etc., should be done with a light but determined touch, and avoidance to over tightening for fear of stripping a bolt is a necessary precaution.  

13. Clipless pedal discussion.  As you noted the advantage of using the inappropriately named clipless pedals (because we actually clip in to them, but were named as such to avoid confusion with the toe cages that people use, but were once known as clips) is to engage the full pedaling circle.  Without some way to affix our feet to the pedals and keep them from lifting off the pedals, we lose the upswing of the pedaling circle.  A great way to begin to become comfortable with the idea of being attached to your pedal and bike is by using the toe cages i referred to above.  Toe cages are made from steel, compatible with your Dragon's pedals, and your foot is kept in place with a leather strap.  While I have clipless pedals on my Dragon and other "race/serious face" bikes, I use toe cages, also called rat traps, on my most very favorite fifteen year old Surly Steamroller fixed gear bike (yes, i'm a little crazy, and certainly appreciate the beauty of coasting on modern freewheeled hub bikes, but there is nothing like riding a fixed gear bike to increase strength and handling on the bike).  You can find the cages here (MKS is my favorite cage and pedal brand, a Japanese bike accessories maker that's been in the game for years), and the leather strap here.  Cages are made of steel or plastic; steel is better and more durable.  Straps are made out of leather or nylon; leather is better and more durable.  Your fear of not being able to unclip from a clipless pedal setup is not unfounded and extremely common.  I learned to use my clipless pedals while riding on some grass, so that when I failed to unclip in time, I fell on grass instead of pavement.  Even today if I have some brain fog or I'm day dreaming, I've forgotten to unclip and taken the slow fall of death embarrassingly at a stop light.  But that also said, should you need to extricate yourself from the clipless pedals super quickly, the pedals are made to allow you to pop out of them in the event of a crash or some significant shock like from a car.  The cleat, which is attached to your shoe with screws, clips into the clipless (sigh, stupid name) pedal using a spring system, very similar to a ski binding if you've ever skied.  So when you are enacted upon from an external force and perhaps ejected from your bike, you'll unclip from your pedals and bike.  I can't imagine my description of the clipless system is probably doing much to assuage your concerns; but most likely the speed with which you advance as a rider will dictate how quickly you upgrade to clipless pedals.  I would bet that in a few months you'll want to get more out of your bike, and clipless pedals are the best way to achieve this.  That said, nothing wrong with sticking with the rat traps, like I said, I've been riding with them on my fixed gear for decades, and I take that bike out for multi hour rides.

14. Bike stand.  If you plan to stick with cycling you'll want a way to get your bike off the ground to be able to adjust things like brakes, the derailleur, or perform most any of the maintenance work on your bike.  Even if you only ever adjust your brakes or clean your chain, and let the mechanics do the rest (that is my method), a bike stand makes life easier.  Again Park Tools makes the best.  The cheap bike stands really suck; a bike stand should be able to keep a mounted bike balanced without tipping over while you hand crank the pedals.  Most of the cheap bike stands do not accomplish this task at all, and in fact can cause an issue for you and your bike should the stand tip over.  My buddies and I have tried many different styles and brands of bike stands, and the Park Tools PCS-4-1 I linked above is the best.  Not overly expensive (but also not cheap, eek), but very very stable.  The other Park Tools stands are unstable or way too expensive.  You might luck out and find one on craigslist or at a garage sale, but the purchase can certainly wait, I just would highly recommend avoiding the cheap ones.