I did my first build about a year ago. I got my lower from Palmetto State Armory and most of my parts were from del-ton I think. I spent a little extra and got a LPK with a magpul MOE grip and stock and I'm very glad I did.
Anyway my main advice would be to spend a little bit of extra money and buy top of the line parts. The LPK and BCG won't cost you too much more but a good upper is going to cost a noticeable amount more. Overall I'd say a top-quality build will run about $200-500 more than using cheap parts depending on your build. Where you can save money is the stripped lower, one is about as good as another if you're talking forged which is the standard. A milled lower is going to give you a unique look and more strength but it will be over kill. Last year before the panic my two PSA stripped lowers were $80 each plus shipping. It might be prudent to wait and see if prices come back down. M4carbine.net has a lot of valuable info on builds, what to look for parts-wise and why.
I put mine together with an old claw hammer, a leatherman, and some punches. I have a collapsible stock so I also needed a stock wrench which wasn't expensive. Had it together in maybe two hours, probably less. I watched several videos online of how to do it before I even ordered my parts until I could almost build a kit from memory. Still I set up my laptop and watched the video again as I put it together and ended up pausing it and rewinding a lot. Every builder will tell you to get a receiver block that clamps into a vice and that's good advice, but I didn't have a vice and I got it together without much issue.
For caliber I'd start with the classic .223/5.56, though most builds should be pretty much the same.
I don't collect guns, I accumulate them.
Last edited by bigghoss; January 31, 2013 at 12:51 AM.