Honestly, most of the Clothing in Echoes of Wisdom is just for cosmetic purposes. As such, there isn't really a "best" piece of clothing. But there are a few that are very useful.
The Silk Pajamas is probably the best overall clothing in the game as it speeds up heart recovery. It's a nice little boost, too, and doesn't have any other drawbacks, either.
Otherwise, the Dancing Outfit is great for mopping up those final Heart Pieces and Might Crystals.