Supply Coins are a valuable in-game currency, and you’ll need to get your hands on many of the seasonal items and challenges introduced in The First Descendant. What’s on offer cycles in and out with the start of each season, but you can typically expect to spend the coins you earn on various types of skins and select emotes as Nexon brings new content to the table. Coins themselves aren’t so easily obtained, though.
https://screenrant.com/first-descendant-how-to-get-farm-supply-coins/