It depends on what your goals for the rifle are. There are very many combinations that range in price and functionality for certain situations. Make sure your lower will accept mil spec parts because civilian lowers can be quirky with compatability of certain parts.
Good brands - Colt (good luck finding any), DPMS, Rock River, Bushmaster, Olympic Arms are a few. Sun Devil and POF are two billet receivers that I know of. I'm currently building a Praire Rat rifle using Sun Devil receivers.
You can build a rifle that costs any where from $700-$800 to over $2,000, just depends on the parts you use and what you want out of the rifle.
I know this is a little vague but if you look at all the options out there, you're going to have to make your own decision. The lower receiver is the only part that has to be obtained from someone with an FFL. The rest can be bought out of a catalog or off the net.