Honestly, the screaming deal in the market right now is the CMMG bargain bin rifles. If you're not dead set on building it yourself but want an excellent starting platform then these are the most economical way to go. While I'm not a fan of S&W's politics in the past, the M&P15 series is another good way to get into a fairly complete rifle at a reasonable cost.
I don't mention Bushy for a reason.. I haven't had a ton of luck with the newer ones. Don't know what their bag is, but as noted by many many folks, they're hit or miss of late.
DPMS is another hit or miss lower mid level manufacturer. Not one I'd buy a complete rifle from. Their lowers are in spec though. Their Lower Parts Kits are entry level and are often replaced after a person learns what they really want in their AR.
STAG makes another great entry level rifle coming in around $825.. they're coming with Midwest Industries BUIS, having fingered one on Saturday I'd say they are pretty decent - the BUIS that is, STAG I love - better than ARMS, but not Troy or GG&G. They're also coming with a mag, so that gets you started as well. I own a STAG upper that's serving well, snagged that from Pete at AR15SALES.COM a while back.
RRA makes a great mid priced rifle as well. I own 2, a 20" and a 16" middy. Both are very reliable and I'd buy another. Don't buy in to the DEA hype.. just because they did a bulk contract with them doesn't mean that you'll get even close to the same deal the DEA and other agencies did, there are significant differences in what the DEA can afford and dictate.. RRA is capitalizing on the marketing hype and if I were a betting man, keeping their production numbers in check to boost the idea that they are a bigger seller than they really could be. Still a great rifle..
CMMG, the bargain bin guns are from what I'm seeing, typically built on DPMS lowers, but as you can tell from most of your research, as long as the lower is in spec you're pretty much good to go. As for their branded rifles, again great reviews and a dedicated customer base.. not to mention they're great folk.
LMT/Novesky/LWRC/Colt - the fact of the matter is that you do get the value out of the costs for these weapons. They are the premier manufacturers/assemblers and they are in that top tier for a very good reason.
You absolutely get what you pay for in a new weapon. There are other manufacturers that I'm neglecting to mention and I'm not hitting the detail that our sticky post has, but one serious piece of advise is to take 90% of what you find on ARFCOM with a grain of salt. You can check here and M4carbine.net for much better and timely information. ARFCOM is a great shopping resource though and don't neglect that!