Planes of Tlessa comes with some currencies that can only be earned by playing the game.
You cannot under any circumstances use real world money to earn currency.
There is also no way of trading currencies between players.
Gold is used for the market board, at the shop and for purchasing additional kingdoms.
Gold dust is used for conjuring, be it public or private, celestial entities. Gold dust is also used in creating alchemical items.
Shards are a form of currency only gained by defeating celestial entities.
These are used in Alchemy in crafting alchemical items.