You'll need a stripped lower ($80 +-) a lower parts kit ($60-$200 depending on trigger) a stock/buffertube/buffer ($60-$300 depending on how fancy, I'd get a cheap 6 position Tapco kit for your first one, then upgrade later.) and a complete upper, make sure it comes with the bolt and bolt carrier ( you can build the upper yourself, but it's more involved and a vise block and torque wench come into play, and it can be a real pain sometimes). Then all you need is a couple mags and maybe sights or a scope and mount.
You should be able to put the lower together yourself if you are even a little bit handy. Go to AR15.com and get the instructions for a lower assembly. Tons of pics and very easy instructions to follow, plus most of the parts will only work one way anyway.
Look for used uppers here or on PredatorMasters.com. There's always a couple around used that are still pretty nice, and it'll save you a good bit of$$$. Don't be afraid to ask questions, there's a ton of guys around here that are literally AR15 experts, and most of them are happy to help get a young guy into shooting more.
