I wore a cup the first few times, but it really just slows you down and chafes when running. If you're wearing decently thick pants/underwear, that's usually enough protection to cushion any hits. I do wear gloves and a neck strap, but I pretty much wear short sleeves and even sometimes shorts as it gets hot. Most normal places will have a fps cap so it's not likely that a hit will break skin. Once things get going, you'll probably so pumped with Adrenalin that you won't feel pain from the hits right away or as strongly as normal.
Expect to go through air and ammo fairly fast as you probably won't hit much the first time or two you play.
Try to stay mobile. If you spend all your time huddled in a corner trying not to get hit some guy will flank you.