As a wise man, or is that Wiesman once said, AR's are kwikfit kits, so anyone can build them.
Some people can even build them to "last 1000 years".
There are too many choices, but if you really want a rifle, then a std one for starters will do.
All this "I want a rifle for PR" etc is bollocks and all you will do is spend too much on something that you might not even enjoy or excel at.
If you really are interested, get a basic rifle and an intermediate scope and spend your extra money on ammo and range fees.
Practise, practise and practise some more, and you will find as you do all this practising, what you like and dislike about your set-up and what needs changing and what doesn't.
Don't waste your money on an "all singing and dancing" rifle. If you're just getting into it, you won't do it justice.
I seriously mean this.
Mark