Here’s a few shows and brands that I trust and use to find good products at good prices. Bear in mind you’ll need a few tools to assemble the upper without scratching things. A set of vice blocks are mandatory, especially on the upper to torque down the barrel nut. Mine are Palmetto State Armory brand, but there are many like it. Get a set of roll pin punches. Avoid Wheeler. Mad in China. Very soft steel. Lyman have worked well for me for dozens of builds. MidwayUSA and Brownells are great sites to buy tools from, as well as some parts and pieces. Primary Arms has a good selection too, but if you know what you want and want to find the best prices, you gotta search a bunch of sites that have slightly better prices most of the time. Not always, and they’re not as easy to browse, but if you already know what you want, sometimes they offer better deals. Schuyler Arms has good sales around holidays on Aero Precision and VG6. B. Kings Firearms has a lot of Aero and Faxon products, but you already have a barrel, so you don’t need Faxon ones. Arm Or Ally, Right To Bear .com, Ballistic Deals .com, Granite Ridge Outfitters, Joe Bob Outfitters, and Lanbo’s Armory are all good places to check prices and shipping.
For name brands, Aero Precision makes great receivers, barrels, handguards, and BCG’s. Top notch. You’ve got so many options in handguards though. Look around. The sky is the limit. For not to much money though, I’ve bought three or four UTG Pro ones, and have to say I prefer their M-Lok handguard to several more expensive ones like Midwest Industries and Yankee Hill Machine. BCM makes good stuff, but kinda spendy. Spikes Tactical is just overpriced Aero Precision for the most part. Toolcraft BCG’s seem to work fine and be affordable, but I’ve never had any issues with a few I’ve gotten from Palmetto and AIM Surplus. My favorites are FailZero EXO coated, though. Buy a nice trigger. Palmetto had actually very nice standard ones in their classic LPK’s. Never tried to save a few bucks and get their Freedom line. ALG ACT or QMS, LaRue Tactical MBT 2S, and Rock River Arms’ 2- stage triggers are gray, from what I hear.
Whatever you do, don’t buy anything made by Bear Creek Arsenal or Radical Firearms. Shitty QC, bolts break, problems, problems. Don’t buy anything not name brand. Bob’s super tactical doohickey is a rebranded Bear Creek or Chinese-no-name clone that’s rough as hell, out of spec, or made with cheap Chinesium pot metal.