The first thing I do on any of my AR's is put a GOOD trigger in them, 15-22 included. But, I didn't want to spend $150-$250 on one. I picked up this Rise Armament RA140-SST trigger from Optics Planet when it was on sale you under $67.00 delivered!! Even at the regular price of around $130.00 it's a pretty good trigger upgrade that's well worth the price. Easy drop-in installation AND ot came with the proper size anti-walk/rotate pins. I have no complaints about it.
I also put this Tru Glo Omnia 4 scope on my 15-22 . Great scope for the price. It has target turrets, tactical illuminated reticle, and, comes with flip-up covers, throw lever, and mount.