The bare minimum is eyepro, gun, battery, mag, and bbs.
Here's what I recommend.
Locust style goggles with foam removed
Metal mesh lower
Gloves of some sort (preferably padded or hard knuckle)
A basic g&g m4 platform
Red dot sight
7.4v lipo battery (or two)
When you go to a game, don't be hesitant about talking to some of the more senior players (by that I mean most of the guys decked out in full gear) and ask them about their gear and guns, some of them may be willing to let you handle their guns to see if it's something that feels comfortable to you. Stay away from anything bolt action for your first gun. If you show up with your own gun already bought, go and ask the senior guys to show you some of the key features on your gun. (Hop up, adjusting sights, etc).
Find out who some of the gun docs/techs are in your area ASAP so you will know who to contact if your gun stops working.
mk43, ump.45, p90, barret, m14, g33, k98, m4 tac, m4 swat, mp5 navy, vsr10, p226, m9.