I've heard great things about the sig Romeo and Juliet combo, it's a red dot and magnifier combo but kinda pricey. For a scope I really like Bushnell's AR lpvo scope, it's a 1-4 magnification and the reticles set up specifically for 223/5.56. For ammo either 556 or 223 would run great in this. I don't own this but in my 556 AR's I usually run 223 cause 223 has a better selection of ammo. And lastly this will take any standard AR magazine, I recommend Magpul pmag magazines since I've found them most reliable.