@sakurish
The avatar product id. (For gumroad, this can easily be found by running a simple curl command, after which it will tell you the correct product id. For payhip, it'll tell you on the download page after you buy the avatar.)
The license key. (You get this after purchase.)
VRChat Username. (The username input is provided during purchase, so use what you input in there. Case & character sensitive! (note: vrchat usernames are stored lowercase!))
VRChat Display Name. (Case & character sensitive!)
Avatar name. (The avatar's name.)
Platform. (Depends on where you bought the avatar, can be either gumroad or payhip.)