I'd follow the above advise to get a list of tools and parts to build the 223. Watch some videos. Go to large gun show and buy what you need and shop the Internet.
The action is a bit tricky and that was the hardest part for my build. I'll admit I bought a completed upper though.
Don't need a billet really.
Good workspace, good tools, good lighting and Red Bull are absolutely necessary.
If youre not too tool savvy, just buy rtf.