I agree with Mike, most of the "tactical" add-ons you see in magazines are crap. I'd look at getting more quality magazines and a good sling. Then maybe a good optic.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
You'll remember the quality of a gun long after you forget how much you paid for it.
US Army 1966-69, VFW Life Member, Retired Geek