I think the skins should be unlockable with game's money, ala R6 Siege though. That is make it not so pricey for people who buy it as a DLC (something like 0.5$/€ a skin should be fine considering they're mostly reskins, maybe 1 for the more "advanced" ones like the prussian skin of Lycus), but extremely pricey for people who buy it with gold, something like 20k gold would be fine IMHO
maybe 10k is even enough considering most people will want to use that money primarily for weapons, locking cards, and loadouts (and later on, recruiting)