Define "build". Are you going to start with stripped receivers and assemble EVERYTHING (component build)? Or, are you looking to slap a complete upper and complete lower together and call it a build (Major Assemblies Build)? If you are looking at option 1 the you have a laundry list of parts to buy and the options are endless. If you are looking at option 2 then the list (in my view)is short.
In no particular order.....
1. Daniel Defense
Actually, I would probably use the same list for a component build as well.
Disclosure: I don't own anything from any of the above (except a BCM Gunfighter charging handle). But if I had it to do over again I most certainly would. Should the opportunity to build another rifle present itself I will.
This really isn't something to jump into blindly. Do your due diligence and research every option before you drop a wad of cash. Start bare bones basic and buy the highest quality you can afford. Then go shoot the gun. Then start trying to figure out what kind of add-ons you NEED as opposed to want. ie quad rail, light, optic blah blah blah yadda yadda yadda. I personally wasted a lot of money on things I wanted, that now sit in the closet because I found they were useless for my ACTUAL NEEDS.
Research, study and take everything you hear on these boards with a grain of salt. Sift through the "ADVICE" you get and verify every claim before you base a decision on it.
When injustice becomes law, rebellion becomes duty.