I've had success with these brands: Colt, Olympic Arms, DPMS, Bushmaster, Armalite, and Eagle Arms. Frankly, it's all hype, all the information on premium or percieved premium parts. Then again, I'm only a competitor with about 2000 rds downrange each season. I am not an operator whose life depends on the boomsticks, FWIW.
I like Westicle's advice: buying a complete rifle like a Stag, Armalite, RRA, Colt, Eagle Arms , etc initially. As your comfort level grows, consider building some upper receiver projects and then venture into the lower receiver addiction(s). Loads of fun.
Then finally, GET OUT and compete with your black rifle at your Provincial Rifle Association's Service Rifle or local GC's 3 gun matches!!
Just don't buy some LaRue, Noveske (hey, I do wear a Noveske hat

) , LMT, Knights , or other exotic boomstick and then STARE and yourself in the mirror while wearing your 'doorkicker' outfit!

Too many of those airsoft (flame suit ON

) wannabees buying the AR's and then not coming out to my matches! (extra high temperature flame retardant applied

).
Hope this helps,
Barney