You should really consider making your own. It's not mechanically difficult, you learn a lot about your rifle and it only requires tools that every AR owner should have for maintenance. You can either save money or increase reliability by rolling your own for the same amount as complete rifles from major builders. Barrel and trigger are where you should spend the most followed by bolt, upper receiver, then lower receiver. Make sure the rail is free float but otherwise it should be task oriented.
Optics/irons are a whole other story. Some would suggest you get used to irons but I'm leaning away from that now. Dual optics (scope and off-set dot) just offer far too many advantages to ignore. If you do decide on a scope buy the best you can afford that suits how you will most use the rifle. I've seen people put 1k+ scopes on ARs they only plink with, and others put 50 dollar knock offs on rifles they intend for self defense. Simple common sense suggests a happy medium.
IMO Satern barrels are the best followed by Noveske, Krieger, etc. For a decent value barrel I would suggest Rainier arms. For triggers it's hard to suggest anything other than Giselle but there are some decent alternatives I guess.
“Bolt” should really read BCA (bolt carrier assembly). NP3 coated BCAs minimise the most commonly held flaw (residue buildup then jamming) of the AR platform.