SomeJoe:
I purchased a custom Avatar and it don't show any different than the original Avatar.
I clicked and saved but it don't become the Avatar.
K7JBQ:
If you're playing on mobile, it won't. Everyone is gray on mobile.
If you're playing on PC, you have to choose it from your appearance tool.
So, apparently, most of your reply is correct.
Avatars can be purchased in the website Pro Shop, not in the app. They can only be selected on PC, not on mobile. IMHO, mobile players should be excluded from buying them or warned in the description, at least refunded on request.
OTOH, there are left-handed avatars on mobile but not on PC.