My first rifle that I purchased was a G&G CM-16 Raider (M4). I took my time trying to figure out if it would be a good purchase and what would work best for me as a starting rifle on my budget at the time. Mine was about $240 from the store I purchased it at, and many players on field I have talked to have said its a great choice for a starter rifle. I've even seen a few of these guys have one of these rifles as a backup in their vehicles. Being a bit shorter than a standard AR, it won't pack quite the same range, but the rifle holds its own and I haven't had a problem with anything about it for the several months that I have owned it.
That's my $.02 - the CM-16 may not be the best choice or prefered rifle by you or others, but just felt like throwing that out there as to what worked for me, an still does.
Like the others have said, once you get AV'd, many doors will open and a plethora of advice will become available to you. Im still waiting for my AV to be approved since I met the verifier a month+ ago. Lol. XD
*Edit: I also forgot to include that I agree with the above post by MultipleParadox. It is definately worth it to wait and have enough money for the rest of the rather important gear, such as a good mask or full seal goggles, and a vest or harness. I was able to purchase the rifle that I did because I had switched over from paintball, and already had the majority of gear that I would have needed to go along with the rifle. :3