This achievement requires you to collect 60 Costume Balls.
These Costume Balls are floating crystals that are generated in different places throughout a game. If you play 2-minute matches, they will appear around the 1-minute mark. They are easiest to collect on Plunder Island - Outside. There are a total of 72 you can collect, 24 heads, 24 faces, and 24 outfits.
NOTE: The computer is able to pick them up
Video Guide:
Credit to KingSuperOne