Guild Wars 2

In the gem store, along the full sets for 800, there could be separated pieces of them going for 150 gems for feet/hands/shoulders each and 200 gems for helmet/body/legs each. It would be ideal for those who like to mix and match their armor.
This way, buying a set through separated pieces in multiple purchases would cost 1050 gems, so it would still be convenient for those interested in the full set altogether in a single purchase for 800.

Support

I really like the boots of the trickster armour for my fire elementalist, but hellz-to-the-naw am I paying 800 gems just for those boots!

Great suggestion