I'd recommend not buying anything, take what you have. The match will teach you what you need. Don't let people talk you into expensive guns and gear until you reach the point where you out shoot the one you have.
At every match, regardless of type, the other competitors and range staff will help out new shooters.
Ammo doesn't matter much as long as its reliable. But for steel matches take twice what you think you'll need. It wont spoil if you don't use it all.
I can guarantee three things are gonna happen:
1: You'll learn something
2: You'll have fun
3: You'll meet great people.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071