My glove choice depends on season. It gets hot and stuffy enough where I live that full fingered gloves are FAR too hot for me in the summer. I wear 3/4 gloves in summertime conditions. I pull out the full fingered gloves sometime in the fall, and once it gets really cold in winter, switch gloves again. I have a couple pair I will wear in wintertime depending on conditions.
I don't like keeping stuff on the bike for typical rides. I have a tool roll that contains everything I need for any ride that I can move from a small pack if I'm doing short rides, to a larger pack if I'm riding farther and need to carry more food/clothing. If I go bikepacking, tools still stay in my pack, though I'll hang some of my camping gear on the bike. Basically, if it's prone to rattling around, it goes in my pack. There ARE some toolkits that are SHAPED like a bottle that keep things from rattling around that you might consider, but I wouldn't just toss my tools into a regular bottle to store them.
I recommend a small first-aid kit, also. Mine has mostly bandages, but also a tick key, some meds and ointments for insect stings and minimizing allergic reactions, pain meds, moleskin, and a few other things. I have used it more on other riders than myself, but the dude who cased a drop and face-planted onto an old dirt roadbed was thankful for my collection of absorbent gauze he could use to mop up his bloody/broken nose while he was transported to the hospital to check for head injuries.
Some glasses are also good safety gear. You can spring for fancy photochromic lenses and ventilation if you have the budget, but you can also do quite well with clear safety glasses for a few bux at the nearest hardware store. I can't count the number of times I've taken a branch to the face, or my tires have flung up a rock or piece of dirt that has hit the lenses on my glasses, or the times I've gone without glasses and regretted it because I got something in my eye. Glasses of any kind are well worth it.
For tire repair, I carry a pump on the mtb (in my pack in the tool kit I carry). The CO2 cartridges stay in a seat bag on my commuter/road bike. With the pump, I have a spare tube in addition to a patch kit. Sometimes you're unlucky and double flat, or you flat your spare tube. With some patches, you can patch up a tube if you are out of spare tubes. They can also patch a tire casing if you're tubeless and can manage to reinflate the tire on the trail. For that matter, I also have a tire boot that's bigger/more robust than a small patch, that is for sidewall tears in the tire casing that even a tube would protrude from. In a pinch, energy bar wrappers can be used for this, also. I also carry a small refill bottle of Stan's sealant because I do run tubeless and if I can get going again without using my spare tube, I will.
In my toolkit is a typical bike multitool, but also a small leatherman with pliers and a knife. Also some zip ties and some duct tape. All of these items have been useful at some point. The zip ties and duct tape are cheap and you probably already have some around the house or garage.
What you wear when you ride depends somewhat on when/where you ride. Synthetic fabrics and wool are what you should be wearing. Don't wear cotton on the bike. You can get fancy bike specific stuff if you want, or you can go low budget and just wear cheap synthetic t-shirts and shorts. I do a combo. I wear nice bike-specific shorts. I have lycra with nice chamois that I wear for long rides and that get used as part of my winter layering with other things. That point where your body touches the saddle is an important one to keep happy. I like to wear baggies, so I have some nice, durable, comfortable, bike-specific ones that don't snag on my saddle when I'm moving around on the bike. I wear them over the lycra shorts. Some will come with their own liners with chamois. The ones I have did not (NZO Dobies, made in New Zealand). The Dobies have a fleece in the crotch area so for short summer rides, I can go without the lycra shorts altogether without chafing on seams. It's not padded so for the long endurance rides, I still wear lycra underneath. Partially so I don't get chamois cream on my Dobies, but also because the padding helps when you're in the saddle for many hours. I like cheap synthetic t-shirts. I have a few bike-specific jerseys, but I find that I don't really prefer them over plain t-shirts most of the time.
Speaking of, chamois cream is nice for long rides.
You definitely want better pedals than the plastic ones your bike has now. Those plastic ones will disintegrate the first time they bang off of a rock, or at some inopportune time when you are landing a jump or drop when you're more confident and decide to get a little rad. The $50-$60 pricepoint is an excellent place to look. Some of the options shown above are exactly the sort of thing you should look at. I have decided to ride platforms full-time now after using them part time for a couple years, and I used clipless pedals for 13 years prior and confident with them. I still have mine in case I decide to do the odd race, but since that's not why I ride, platforms fit my riding better. I use them on 3 bikes, including my road/commute bike.
And less of a purchase item, but possibly depending on how you want to go here, but you should think about how you're going to handle hydration and nutrition beyond just water. If my ride is going to be relatively short and in fair weather, just water will be fine during the ride. But beforehand, I need to make sure I'm satisfied and not going to get hungry on my ride. A snack usually takes care of it. PBJ works well. Depending on how hard the ride was, I might need something after. For some reason I crave big burritos after tough rides. It starts getting a bit more involved the longer I'm out, and the hotter it is (more sweating). I need to think about electrolytes, what I'm going to eat out on the trail, etc. Everyone is a little different and needs to figure out what works for them, but there's a huge range of energy products you can buy, and you can also carry real food and homemade stuff (and you can find recipes for that - there are even a few books about the topic floating around). If I'm doing a winter ride, it might be worthwhile for me to bring my backpacking stove, fuel, kettle, and some coffee/tea/hot cocoa to warm up mid-ride or at the end.
