The basics to Buying a Diamond! I think a 1 carat center stone is the perfect size for a ring. ( not too small or big) personally i think for any decent size stone it should be G color or better and SI1 or SI2 in clarity or better. That way you cant see a yellow hue and the inclusions aren't so noticable. Really small side stones (melee stones) dont have to be as nice because its less noticiable. The cut should always be at least rated Good or higher.