My recommendation is to pool paint for tournaments so everyone puts in 2-3 cases and shoots it throughout the day. Start with everyone buying 2 cases, fill out of the common pool, and then buy more as you need it to keep waste down and make it fair for everyone.
That way fronts don't have to worry about the backs who need to keep them alive being stingy and the backs don't feel cheated just because you only carry two pods into the snake.
how much paint is used can differ alot it depends on a few things such as how agressive you are or your team is. how the other team plays and mostly the field layout. we always pool paint as a team and start out with 2 cases a piece. you can always just start out with a case at a time its easy to buy another case when you need it but you cant exactly take back paint you have opened.