If you want to learn, check out the forums at m4carbine.net and ar15.com. What you'll find is that for complete guns, you can't go wrong with a Colt. It's the standard. There are many other brands with excellent reviews, such as BCM, Noveske, Daniel Defense, and others with spotty reps, like Bushmaster, Rock River Arms, and others. I ended up getting a Daniel Defense M4 v7 and I love it.
I might think twice about building your first rifle. While it is a great way to learn how everything works and fits together, buying a complete rifle from a reputable manufacturer means you get one that works out of the box and in my case, one with a lifetime warranty.
I just about have talked myself into one and I got a few gun magazine "buyer's guide" issues to get a feel for the market.
The number of companies making an AR15 was a surprise, not to mention how many different models there are.
This isn't as easy as I thought it would be.
Naw, with any mechanical skills building ARs is a breeze and they function every time. I’ve built several and sold most of them. Got tired of the usual so I started building piston ARs and Pistol/Piston ARs. That got old too, so now I’m into shotguns, 20 and 12 gauge varieties.