Hi! Whether saving coins for future features, drawing in Eight Inner Gates to level up your Chakra Runes/Get new runes/Save for future redeemable runes, or donation to group. There are quite a few ways to use coins. As you know, Chakra runes do get increasingly more expensive to upgrade, but upgrading them does give you a lot more stats. Also, coins don't really depreciate in value per say, so saving them won't be a bad idea either =p

~Jib