Anyone training in a combat sport should take a moment to assess the equipment they use. As with most things in life, you get what you pay for and if you plan on making a career or long term commitment to a combat sport you really should drop some coin on professional level accessories. If you are on a budget however, it is wise to devise an order of importance so you might upgrade from shitty equipment one thing at a time. For the sake of discussion I separate my gear into two categories: things that keep me safe and things that keep my training partners safe. Of the two, it is MUCH more important to invest in quality items that promote personal safety and health.
For any given fighter, the most important decision you'll make is what headgear and mouthguard to buy. Whatever you do, DON'T go for the cheapest you can find in EITHER of these assets. Protect your braincells and your grill at whatever cost. I suggest the higher end Fairtex or Title headgear. Don't just order one online, try and get into a store so you can try a few on and see how they affect your vision. Also, make sure your ears don't fold over when you move it from side to side, this will almost certainly lead to nasty cauliflower ear. Check the quality of what it's made of, leather and any shock-absorbing and/or antimicrobial features are key. I know so many people who buy the 20$ headgear at sports authority claiming, "it's all the same anyways." Every time they come in to spar not only do they get rocked by any looping punches due to lack of peripheral vision, the head set usually ends up repositioning and blocking one or both eyes and pinching their ears. The ideal headgear not only protects your braincells, but when fit correctly, doesn't get in the way of your training.
As for a mouthguard, protect your jaw and teeth my friends. Don't spend 5 dollars on a piece of rubber, if you're going to go that route, just get a piece of rubber at the dollar store and bite down. I personally use and highly recommend the Shock Doctor Ultra 2 STC mouthguard. It covers only the top set of teeth which I prefer for endurance and breathability. This mouthguard will keep your jaw secure and won't fall out or become loose if you try talking while you wear it. Dental insurance is not common among fighters and the proper mouthguard will not only save your teeth, but protect your jaw and decrease the likely hood of being knocked out and losing many much needed brain cells.
Now above I mentioned that the headgear and mouthguard you choose are the most important for "any given fight," partly due to the fact that I am including female fighters in that statement. For a male fighter, however, the cup and compression shorts you choose may be of equal if not greater importance. For a long time I used the shock doctor compression shorts with the hyperflex cup, but no matter how safe I tried to be I never managed to make it through a training session without one of my testicles being savagely crushed between my thigh and rim of the cup. This is when I switched to the Jaco Guardian Protective Cup system. Not only is the cup shaped in a way the my package has a chance of staying in, the compression shorts are fit with velcro straps in the front and back that secure and fit the cup to your particular body. THESE THINGS FUCKIN ROCK! Even when I get a flush kick to the groin or someone rams their knee across my crotch while doing jiujitsu and wrestling, my package remains unharmed. This is an incredible peace of mind for those who want to have kids, and are afraid that every time they throw a front kick their nuts will be fed to their stomach.
Lastly, among things to protect yourself are ones that vary greatly in price, but not so much in benefits to your health. Wristwraps, grappling pants, rashguards, braces, supplements and other like items all fit in this category. One thing I will say about these things is this, USE THEM and USE THEM ALL. 180" wristwraps will keep you from breaking your damn wrist and allow you to put some power behind your strikes. Grappling pants and rashguards will keep your skin healthy and help prevent disgusting fungal infections all over your body. I prefer longsleeve rashguards and full length grappling pants not only for the sake of improved grip when I get sweaty, but for the sake of my training partners. These two items will keep your hair from getting all over the matts and in the eyes and mouths of your teammates. They may not ever notice what you're doing is for their benefit, but if they did, they would bow to you.
Regardless of whether you NEED braces, I recommend using them. Our joints go through far more wear and tear than the average human being so wearing a brace on both knees and ankles is a way to say thanks to your body for enduring the horrible treatment you impose on it. I recommend a multi-vitamen to all human beings but especially to fighters. Nutrition is key to building the best machine you can and a multi-vitamen helps pick up the slack where you fuck up. Other supplements I use are b-12 and b-6 for energy metabolism and hyaluronic acid and glucosamine/chondroitin for collagen and joint health.
To end this discussion I want to address the topic of not which gloves or shinguards to use, but what to look for and HOW to use them. The proper combination of insteps and gloves not only protect you but your training partners as well. First of all, I hate shinguards that are held on by a sleeve. Not only are these a severe pain in the ass to put on, but after you've sweat in them for a couple hours they're nearly impossible to remove without putting incredible strain on your joints. Velcro straps make it much more efficient to put on and take off shinguards when needed and have the benefit of being easy to clean. Also, don't buy the cheapest, most thin shinguards you can find. Not only do these end up falling apart, but the padding they use becomes so dense that it feels like you're being kicked by something far worse than a shin bone.
When you buy your gloves, go with a hook and loop system. Laces are awesome for competition but in my opinion they're too time consuming for training purposes. The hook and loop system is awesome because it provides extra security to the wrist that a normal velcro glove doesn't. Also, regardless of what other people in the gym are using, go with 16 ounce gloves. They will keep you from breaking your damn hands, protect your sparring partners, and when you switch to competition gloves you'll be much quicker than you would have been had you trained in light gloves all along. Lastly, don't use the same gloves you do for sparring that you spend countless hours beating on a heavy bag. This may be the biggest dick head move in all of combat sports. You might as well leave them in the freezer before you train because that's what it feels like. You effectively condense all the shock absorbing material in the glove into a nice solid brick of leather. While this may still effectively protect your hands, which I submit is not the case, you will certainly lose sparring partners every time you land a solid shot.
On a final note, I hate not to mention the importance of hygiene. Disinfectant sprays, wipes, foams and germ-x are a fighters best friend. A good disinfectant spray will keep you and your equipment healthy and more pleasant to the nostrils. I spray Regency Professional disinfectant on my gloves, headgear, and shin pads after every session. Furthermore, I use athletix wipes up and down my arms every time I put on and take off my gloves and on my neck and behind my ears when I've been grappling and on the matts. I hate it when people don't sanitize their hands before grappling after two hours of wearing boxing gloves, I can practically smell disease. Furthermore, encourage your training partners to do the same, and if your gym isn't as consistent with sanitation as you like, take matters into your own hands. It sucks so fucking bad when you smell last weeks sweat on the matts, it's like playing Russian roulette with staph, ringworm, athletes foot, impetigo and herpes all in the chamber.