So what would the rules be if this was a category? What items should we buy from each shop (The exclusive shops and normal shops)?

A lot of outfits only unlock until after beating the game, including the Skeleton Suit, but the main issue would be outfits that unlock at a high number of moons (spanning all the way to 560). As a result, this task would be really similar to a max% pre-credits, similarly to Bridal Taunt% which would require 460 out of maybe 461 possible moons

Idk, its looks like a 99% speedrunner

Id run this for the memes

So only those items from yellow shops that are only available in one kingdom? Sounds solid; kinda close to All Purples; excluding souvenirs would make it All Purple Coin Outfits + more shop time; alternatively imagine All Souvenirs as a Some Purples category