Save enough money till you have about $1500.00 - $2000.00
Seek and find one of the following:
LMT
Daniel Defense
Colt 6920
BCM
Noveske
SPIKES TACTICAL
STAG with $100.00 "Plus Package" milspec upgrade.
Smith and Wesson Mp15a (has 1:9 twist)
You are looking for HPT/MPT barrels and bolt carrier group. Chromed 1 in 7 twist barrel and 5.56 Milspec chamber.
Watch Brownells for sales on their Milspec grey magazines with green followers. OR Magpul P-mags.
Buy 10 of them...$150
Buy an EoTech model 517....~$400-450
You'll be happier if you wait and buy one of the above. Cheepie AR's that are non Milspec aren't the same gun as a proper spec built one. The quality magazines listed... work. An AR is only as good as it's mags. With out them it is a single shot.
The Eotech is a good optic as is Aimpoint. Either will do you fine.
Armalite is not the Armalite of yesteryear. They aren't the quality of the guns listed above..
Check with
www.ammoman.com or
www.ammotogo.com and buy 500 or 1000 round cases of XM193 (55 grain) or M855 (62 grain) ammo
The above might be more than you were braced for but if you are serious about getting into a good AR that will last you and is something you can bet your life on. IF you want a plinker your fine to go with Bushmaster, Armalite or DPMS...in that order.