Piebalds, but you would need more money than that to pick up a male and 3 het pied adults.
In the price range you listed--go with Enchi, or, if you can, an Enchi combo. Enchi is definitely hot right now, and will be for some time to come, since it makes amazing combos.
I assumed you wanted to pick up adult females, since you were looking at what's popular right now.