Another vote for Colt.
My first AR was a Lewis Machine and Tool- at the time I lived in California and it was the closest thing to mil spec that could be had in the state. It's a sweet shooting rifle and is solid, but above what you're looking to spend.
I also have a few different ones built using PSA parts, a mid length 16" and a 10.5 pistol. Both a lot of fun. Zero malfunctions with either. Pretty amazing that these days you can get great performance even with inexpensive gear.
I did build an 18" rifle gas system gun with a carry handle upper and fixed stock. Has the clean, classic lines and is fun, but the flat top upper on 99% of the guns you'd buy today is much more flexible.
Then there's my Colt. It's a utilitarian and no nonsense expression of what an AR is. As was mentioned, just because it's made by the same company that supplies the military means when the next scare/ban happens it will be at the top of the "sought after" list. It's everything you need, and nothing you don't to get started with your first AR. The bulk of sales appear to be the 16 inch barrel, although I've seen 14.5 inch barrels with a pinned muzzle device for sale sometimes (the pinned muzzle device results in a 16 inch+ barrel length since that's the necessary length for it to be a rifle and not an SBR). If the same price I'd go pinned 14.5, but it's personal preference. Otherwise, Colt offers them in 20 inch configuration if you're interested in that.
The Colt "Expanse" comes in at a little lower price point and gives up a few features, most notably the chrome lining in the bore. If I were you I'd wait for a sale on a Colt 6920.