Tracer, you need to tell us at what maximum distances you plan to shoot and what size targets you want to engage.
There are far too many scopes out there to just say "get the XXXXXXX scope!"
Since you have a carbine I will assume, for now, that you will not be shooting great distances (not more than 200 yards). In this case I would highly recommend the AMT 5x33L Professional scope. It's a fixed 5x scope with lots of features like: etched reticles (not suspended wire), 10 position illuminated reticles, BDC out to 500 yards (specifically for the 5.56mm round), range finder and coated lenses. All this for about $200.
I have one of these on one of my 16" carbines and have been more than pleased with it. The AMT was specifically designed for the M16/AR15 so it is one rugged scope.
CMOS