Where do you find money(coins that worth money) to pay players in the game?
If you want something like that, you will need to create your own blockchain. Or any new member pay entrance fee and that entrance fee will be a pool prices distributed between players when needed. In return you can send them $3 T-Shirt as the gift for registering on your service.
Most big game worlds, from EVE Online to good ol' WoW, have a currency. Players get it in-game, and spend it in-game. This currency can be a token on an external chain, don't need T-Shirts or your own blockchain. Cheap solution is when only the centralized server that runs the game is a node and converts the token into in-game play money and back, transparent for the players. (don't want them to pay an Eth tx fee for every action in the game)