Eye protection and your main rifle you should never cheap out on
The RIS can be added later, get yourself AVed at TA and lot of people selling goodies on the Classified, see a few RIS and hand grips too.
Ares isn't bad either, has some proprietary parts but the quick change spring is pretty sexy.
I have a Ares M4 and Dboys RDW sitting in my closet collecting dust =D