The barriers for entry into airsoft are definitely lower than say 4 or 5 years ago. I'd say that all you have to do is sign up (ask the host if it's a "noob friendly game") and let the host/other players know you're a noob and need to borrow gear.
At the very least you should have your own footwear and possibly some BDU's even if they're a cheap $30 set of Olive Drab from a local surplus store (that's tunic and trousers). Mask, if it's a paintball venue will have rental masks available and the rest can pretty much be borrowed from other players for say a 6 pack or $10 or something.
I'd say it's perfectly reasonable to pay ~$70 for the day. $15-20 for field fee, $5 for mask, $5 to the guy you borrow BB's from, $20-25 for gun (or just buy the guy a 6 pack and a pizza sometime), $5 for gas money if you're carpooling and the rest for other incidental costs.
PS: THANK YOU for actually asking a proper question in the newbie tank, there's been a lot of idiots who just can't seem to be able to read stuff that's been handed out to them and just post things that have already been answered. I can see you having a great time in the community if you keep up the reading things first before posting attitude.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE