What is the best AEG airsoft gun for a beginner and what else should I get?

I'm just starting out with airsofting and I wanted to get a cheap airsoft gun that will last me a while and not break (preferable full metal) so I don't have to buy another one. I was looking at M16s but any thing that looks cool, has a large battery compartment and won't make me go bankrupt is good. Also what else should I get for airsofting? I have an ACU and I was going to also get a CO2 pistol, a helmet, a crossdraw vest, a hydration pack, some BBs, and spare mags. I have $500 right now and so far I'm just looking around Airsoft GI. Need some help.