1. If chk if that field dont have rule about field pain only. If you going to rent marker on the field, they make you buy their own paint. Also no red paint rule can be apply.
Unless its not commercial field , but somones backyard, so there are no rules.
2. If thats your first paintball, be sure you are going to use 1200-1500 balls in 5-6 hours. So, 2000 case per person is possibly good idea. Dont buy cheapest paint in wally world, they sell monsters for about 24$/2000, thats crap. Good paint cost about 40$ per 2000. But if you dont care about chopped balls and cleaning barrlel all the time, go for it ;-). Also when you buy paint, ask them to open box , balls are broken, pick another box and chk again.
Sports authority have higher prices on everything then wollyworld(at last in my town)
3. My tippmann a5 use 2 x 20oz co2 bottles for about 1000-1200 balls. My gf use tippman 98 custom and she use 9 oz tanks, something around 4 of them for 1000 balls.