The currency used in the Ys series is usually Gold (abbr. as G). However, some Ys games have a second currency, no currency, or an entirely different currency from gold. The currencies are usually dropped by enemies or found in treasure chests in various places in game.
Games that feature currencies other than gold
Enemies will drop Ravals that can be used to strengthen the weapons Adol can purchase or find in game.
Ys Origin is the first game that does not feature gold as a currency since the game is set in Darm Tower, and does not have any human settlements within it at all. Instead, enemies will drop purple gems called SP that can be used to exchange "blessings" at Goddess Statues. This blessing includes buffs that strengthen equipment, replacing the functions of shops in other games.
Note: In later games, SP is used to call the previously unnamed magic meters (now called Skill Points) that is spent to perform skills.
Ys VIII is the first game that does not have any currency in the main section of the game which is set on a deserted island. Instead of collecting gold, Adol and his party collect resources and exchange them for better resources with a barter system.
Special resources like iron ore or orichalcum are required to strengthen weapons instead of a special currency like previous games. A reusable resource, the empty bottle, is introduced to store medicine made.
Ys IX: Monstrum Nox features similar bartering, forging, and apothecary systems, though Gold returns as the main currency as well.