Haha, that's the sacred question. How many. Well, they will always sell them at the field, but you can never have too many paintballs. I always buy a case before I go paintballing, and I usually end up buying more before the day is over. 500 paintballs will not be enough though. Shoot for about 1500 or so. If you need more, buy some at the field. What you have to think about, is you'll probably go through at least 1 1/2 hoppers per game. That's about 300 paintballs per game. Say you play 10 games, that adds up to 3000, give or take. Add the chance of getting shot on the break, short games, and all the other things that could happen, that lowers down to about a case (2000) per 10 games. 1500 should be enough to start with, but you might need more, so bring money to the field.