There are really three things that you need to go paint balling. You need the right clothes, gun, and paintballs. Some paintballs that you can purchase are Monster balls. They are the least expensive but they are the lowest quality. These type of balls are good for target practice but not good for anything else. I wouldn't recommend them. They don't break easily, which is especially bad for tournaments because it doesn't count as a hit unless the ball explodes. These balls also have a tendency to have lumps or divots in them which make them less accurate. The best paintballs are the Impact Balls. They are still a reasonable price but they break on impact and are much more accurate. They also don't break in your barrel as much as other paintballs that I have used.
Other things that you need are the right clothes. Paint-balling is a physically active and so you don't want to wear something really hot. At the same time it is important to cover your skin. A direct hit might break the skin and it hurts a lot worse. I would recommend that you wear a long sleeve shirt, light pair of gloves and jeans or heavier pair of pants. Lots of people like to wear camouflage. This could be a great help but really when your playing the game your eye is looking for movement so I am not sure how much the camouflage helps.
Probably the most important thing that you will need to buy in order to compete in this sport is a good gun. Those that have the best guns win the battle. There are so many out there it is hard to know which one is the best. Some guns are good at accuracy, others distance, some are fully automatic and other only semi automatic. He can buy any type of gun if you have the budget for it. I would recommend either the Spyder or the Tippman 98. Either of these guns wont cost more than $150 and they are durable, made from metal. They both are in the mid range levels for accuracy. If your just getting started and don't want to have to buy a gun in two weeks, then these two guns are for you.
Paint-balling like other sports requires good equipment. One can spend a lot of money and have the best stuff out there or not spend as much and still compete. If your like me and a starving college student then you might try these pointers to get started and then move up from there.