The currency used in Fire Emblem games is gold.
Gold is typically represented in menus with a “G” and pays for weapons, staves, consumable items, and other supplies bought from armories, vendors, and shops. Players usually earn it through treasure, map rewards, selling items, or special activities such as arenas, depending on the installment.
The system is not identical in every game. In most entries, the army shares a communal pool of gold, so any eligible unit can shop with the group’s funds. Fire Emblem: Genealogy of the Holy War is a major exception: characters maintain individual gold totals and can transfer money under specific relationship rules. That difference can make the economy feel very different from later games.
Gold is also easy to confuse with series-specific items. Bullions, for example, are valuable objects that can be sold for money; they are not a separate currency. Likewise, rupees and coins belong to other Nintendo franchises, especially The Legend of Zelda and Mario.