Something you should consider is the PSA Premium / CHF upper. They do runs of uppers with FN hammer-forged barrels, Geisselle gas blocks (pinned to barrel) and Geisselle free-float rail.
These uppers sell for $499 without a BCG. You can get an assembed lower with basic Magpul furniture for around $120 and a BCG for about $80-$100.
Grab 10 PMAG 30s at $7.99 each when they have a coupon-code (they do frequently) and your complete rifle with mags is right at $800.
This will be a solid rifle with a high-quality barrel.
For an optic I'd look at a Vortex Sparc AR. Compact, durable, daylight bright and runs on a single AA battery....not a hard-to-find lithium. My only complaint for the Sparc is the stupid lens caps but that is minor.