Well you're off to a good start. I would recommend skimming through the stickies to get a sense for the process then draw up a list of things that you want to do, i.e. plinking, hunting, target, hog hunter, varmint gun, etc. After that post a thread or update this one and the folks here will be more than happy to recommend a host of options and opinions on the various parts suited to your needs.
A basic build can be accomplished well within your price range. It's is a fairly simple process to build the lower, no special tools are required and there are many good how-to guides posted here and on the web. The upper is a bit more complicated and requires several specialized tools, if this is a one-time project the extra $100 or so may not be worth the investment, in any case it is usually suggested that you purchase a compleete upper the first time and go from there. PSA, RRA, BCM, Daniel Defense, etc are good sources.
Doing the build won't save a ton of money but it will get your a rifle built exactly to your specs as well as a gun that you now have the ability to upgrade and maintain. Off the shelf builds are fine but ultimately you will want more than what the builder has decided to give you and when it breaks, who's gonna fix it.
"The whole of the Bill (of Rights) is a declaration of the right of the people at large or considered as individuals.... It establishes some rights of the individual as unalienable and which consequently, no majority has a right to deprive them of." (Albert Gallatin of the New York Historical Society, October 7, 1789)
"A free people ought not only to be armed and disciplined, but they should have sufficient arms and ammunition to maintain a status of independence from any who might attempt to abuse them, which would include their own government." - George Washington