As far as brands of AR's.... I'd say most any brand would surfice, as a starter rifle.
I bought a pre-ban Bushmaster ( Windham, Maine )as my 1st AR,, just before the Clinton ban took effect .. & paid 2X what it was worth !
Next was a Palmetto State Armory (PSA) carbine kit, that .inc. everything but a stripped lower.
I also bought a PSA stripped lower, & added the kit parts. = my 2nd AR.
Had some issues with this rifle, but I've got a good gunsmith to provide information I didn't know, & got the rifle reliable.
I've recently noticed Anderson AR-15's on sale for $499.00 My guess this would be a good economical starter rifle, and
PSA has been advertising a complete , assembled AR for the same price.
Any Springfield, Colt, other recognizable name brand rifle will work. or if you want a more "premium" brand , with higher quality parts & higher price,
others like the DD brand mentioned. There's certainly a lot of brands to choose from. Usually more expensive will = a better quality AR..
but read below.:
I will add that higher priced doesn't necessarily mean more accurate.
A local AR builder, Combat Armory ..had AR uppers on sale, for cheap. (Learned about the sale on a local gun forum)
I'd never shot cheap, steel cased ammo (i.e. Wolf / Tula) but I read an online test, re: barrel wear of steel core jkt'd bullets in the cheap ammo,
vs lead core jkt'd bullets, & decided I should give the cheap ammo a try. A factor in my decision was that component prices,
had increased to the point that I could buy the cheap , foreign ammo for about what my cost was to load 223 rds.
This was pre-pandemic, pre ammo shortage / escalating prices..when foreign ammo was cheap. I decided to buy the cheap Combat Armory upper,
which included a BCG & CH.. figured I'd drop it on to a lower I already had & use this upper toshoot steel cased (cheap) ammo.
Before I tried the steel cased ammo, decided I should see how accurate it was shooting my usual 223 loads,,
my handloads with lead core 55gr fmj bullets. Imagine my surprise when I shot groups about .5" @ 50 yds...better than my 3 other AR's
I also had bought an Adams Arms AR, to try a gas piston AR, instead of the DI gas system most AR's use.
The C.A .upper shoots better(tighter groups) than the other 3 Ar's I own... Think I paid $169.00 for the upper, BCG, & CH.
Never shot that steel cased ammo I'd bought..sold most of it when the ammo shortage hit, still have maybe 100 rds.
Bought an Anderson stripped lower, C.A. has a sale on a lower parts kit, so added it it to the lower. A CMC 3.5 # trigger,
scope & bipod were later added. Now it's a reliable accurate shooter.