Now that have your first AR15 you'll start wanting all the fancy "Go Fast" gear.
SOPMOD or EMOD or IMOD stock.
Rail system.
New pistol grip. Ergo, MIAD, Tango Down Battle grip, etc.
Light and light mount on the rail.
Vertical foregrip.
Sling mounts in the right places. Two point, one point etc.
Optics with nice high quality mounts.
Enhanced bolt and bolt carrier for better reliability.
SOPMOD upgrade kit for the your extractor.
Before your done, you might even Cerakote the rifle in Deset tan camo, urban camo, Woodland.
It never stops. You might even want to change out the DGI system to a piston install system.
Have fun, this is going to be an adventure for you tricking out your M4'gery. :man_in_love: