Re: ar parts
You dont have anything, so your building from ground up.
*I would go with a Spikes or Mega lower. Ive heard good on both of those.
*RRA internals (2stage trigger)
*I would try to match the upper, so Spikes or Mega upper. Stripped should be under $200 bucks, try Rainer Arms.
*Check out Bravo Company for the BCG/Charging Handle. Usually have good deals on other things also like complete uppers, stocks, handguards, grips.
What kind of barrel are you looking for? SBR, 16''+, then you can decide on what type of flash hider you would like.
Then comes the sights, you want flattop or carryhandle style? I would go with magpul flip up front and rear rights, front mounted on quadraill and get a cowitness red-dot something like an aimpoint, or Eotech (which I will be dogged probably for suggesting) and a good mount for it. Here I suggest Larue Mounts.