I'm not sure what to do with the spirit once i'm done with spa, is there somewhere i can convert it like world boss coins?
You do the same thing as someone who gets skins for collab units they don't have.
Spa goal : Get your Child lvl 100 Likeability When done for one Child, change the Child with another one you want to boost Easy :D
Wow... you're the first person I've seen reach max lvl spa.Maybe in the future, spirit can be convert into a gift.
The highest I have is around lv 41. Puts things into perspective.