To wear a helmet or not is personal preference. Some of us wear helmets, some not. My wife prefers to wear helmets, I sometimes do, sometimes don't. The plastic replicas are just fine...plus they are lighter than the real ones of course. That's what we have.
Most airsofters wear just goggles, as long as they meet the ANSI rating for impact. If you play at Panther Creek Paintball, you are required to wear a paintball mask for their insurance reasons. Don't go out and buy one if you don't have a mask already. They have loaners.
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There's nothing FRIENDLY about fire!