I am a n00b in the AR realm myself. I have wanted an AR since I was in 8th grade. I decided that I wanted to start my mid-life crisis a few years early, so early this year I started seriously planning my first AR rifle.
I had been lurking at AR15.com for on and off for a number of years prior, but finally registered and ramped up the frequency of my visits. As far as AR15.com goes, There is a lot of great info available there, but sometimes you do need to wade through some crud to get to it. Anyhoo, cruise that site for a while, and you'll pick up some good info.
Being n00b, I originally thought about purchasing a complete rifle. But the more I read about the AR, the more the vision of MY rifle took shape in my head. So instead of a complete rifle, I have decided to assemble one - not build, but assemble - by putting a complete lower together with a complete upper. That way I could order the upper exactly how I wanted it. And by doing that, the rifle is more or less set up the way I want it, and I don't have to order a new accessory every pay period for 8 months trying to complete my 'dream' setup.
Purchasing your rifle in parts also makes it easier to spread the cost around. So, $800 may be your limit for a complete rifle purchase, but if you spread that over 4 months or so by buying parts, perhaps you can maybe spend a little more on your setup. Money is always a concern of mine, so the complete lower + complete upper route has helped me manage the rifle budget.
Build from the ground up, assemble complete parts, or buy a complete rifle - either way, I'm sure you'll enjoy whatever you get. But realize that it is a disease. I haven't even completed my first AR project, and already I'm thinking ahead to my next one.