I've found myself going to whatever World FATE gets announced on any of my DC's worlds (at least ShB, EW and DT ones) because they are a good source of the bicolored gems and I just generally enjoy doing these fights. But in the process I've been stacking up the drops from these fight and have nothing really to spend them on.
I would be interested in having something to spend the extra drops on, possibly materia, mats, etc.