In your photo, you see three different styles of glasses, champagne flutes, wine glasses, and martini style glasses. First ask yourself if you have different types of glasses you intend to store this way. Then figure out how many of each style you intend to store and use. An average rule of thumb used to be that you'd have enough china, crystal, and flatware to feed 8 at a dinner party. Although a full set of crystal would be enough to serve 12. Remember that whatever you have out like this should be used and washed regularly otherwise they will start to collect dust.

As you can see in the photo above, they have what appears to be 8 flutes, 15 wine glasses, and 4 martinis. So you don't have to have a full set of glasses out - just the ones you'd use on a regular basis.