Crimson Ingot uses a physical economy. This means that the amount of Crimin you have is solely represented by how many Crimin Coin items you have, and the individual values of those coins.
Crimin coins are earned in Heathrest by trading goods and completing small tasks given by the Commissioners.
Crimin coins can be traded for tools, weapons, food, etc. - anything offered by one of the many Shops located around Heathrest and beyond can be bought with Crimin.