Don't get too caught up in accessorizing your rifle just yet
1) learn how to clean and lube the AR. I suggest the utoob vid by NSSF Clean your AR-15 (Chris Fry)
2) start off with decent brass-cased non-corrosive factory ammo. If you choose to shoot steel cased or corrosive after you learn the differences, so be it.
3) spend some quality time with the peep sights, before you go with optics. Even tho you may only drive a car with an automatic transmission for the rest of your life, you will never regret learning to drive a stick.
4) for a cost-effective red-dot sight, I would suggest taking a look at the Vortex Sparc (utoob vid, military arms channel)
Last but not least, I can assure you that in the long run, learning good rifle marksmanship will be much more rewarding than tacti-cool bling bling on your gat
