Plus one for grabbing a G&G. They are quite upgradable, you won't likely be disappointed. Airsoft guns range from $200 - $3000 or so your budget will only get you entry level guns period, that doesn't mean that they are bad, just not as good as more expensive guns. You can however fully change and upgrade guns like a G&G over time, so it's appropriate. As for which variant you want, well it doesn't matter too much, so get what you want. Personally I'd recommend getting a plain M4 and adding what you want. Barrel length only makes guns long and less functional (in most cases), so I'd also reccomend getting the CQB or carbine length ones, such as an M4 over an M16. Your gun will need good batteries, a good charger, good BBs, and magazines. If you're planning on playing you'll need good eyewear and possibly a few other things to keep you safe and keep you in the fight. Never ever cheap out on things you run in your gun or things that keep you safe. Start putting a little extra away. Spending $500 or more to get you bare bones but field ready isn't unrealistic. There's more to airsoft than just owning the gun.
ďREALITY IS LIKE A STONE. TO MANY ITíS HARD AND COLD, THEY CANíT HUG IT OR EAT IT, IT ONLY FRUSTERATES THEM AND DOESNíT DO THEM MUCH GOOD. TO OTHERS ITíS STRONG AND DEPENDABLE, YOU CAN BUILD WITH IT, BUILD UPON IT, OR WORK WITH IT, ALSO USE IT TO SMASH PEOPLE IN THE FACE.Ē