To be honest with you, a 2 ct diamond won't look like 3 ct and that's why there is a big difference in price. On occasions, a 2 ct diamond can be "spreadish" (have a big table), and that will make it appear larger - nevertheless, it will have an effect on its shine and reflect.

You were suggested to surround it with small diamonds - it's a good idea.
Another idea is to set it within a white gold / platinum ring surrounding it (place the diamond inside a cup). It's usually done with earrings, but still, if you must...

I think that all of the games of making it seem larger would eventually look less beautiful than the classic solitaire ring (even if it's 2 ct).

Good luck!