Everything that used to cost Force Gems is paid with Dungeon Points.
On Pure Cabal you earn Dungeon Points (DP) by playing. Every price that the game shows in Force Gems is paid with DP: the DP Shop, Event Pass levels, Anima Mastery, Merit Mastery and other systems.
Spending DP also counts for the Challenge Mission goal “Use DP” and the Event Pass mission “Earn Challenge Mission Score”.
Costumes are sold only for Mileage.