Buying a Paintball gun?

im buying a paintball gun in a few months. And iwant to know mroe abut them before i buy one. im looking into a Smart Parts Epiphany Paintball. because its at a good price and has good reviews. What do i need besides the gun to get started. and explain what each thing is for please . like do i need all the accesories on sites. Like do i need a cO2 tank. do i need all the vavles, elbows and stuff like that. So please tell me somthings i need and what there for. descriptive anwsers please. =)