Coins are the currency of Super Mario RPG: Armageddon, used to by various items and equipment.
There are three types: regular coins, Frog Coins, and Galaxy Coins.
Regular Coins[]
This is the base currency that is obtained primarily through battling enemies and selling items.
Due to how many coins you can get, there is a shop in Seaside Town that lets you turn coins into Gold Bars and store them at a bank.
Coins are spent in various shops or to attempt certain minigames like Sky Bridge Minigame and Goomba Thumping Minigame.
Coin Fountains[]
There are several items that can be reacquired for free and then sold for a fair number of coins.
Specifically, once you find all the hidden chests, you can talk to the Shaman in Monstro Town for a free Lucky Ring and then sell it for 777 coins. Repeat as many times as desired!
Coin Shops[]
Mushroom Kingdom
Rose Town
Moleville
Booster Tower
Marrymore
Seaside Town
Sunken Ship
Monstro Town
Nimbus Land
Barrel Volcano
Bowser's Keep
Factory
Frog Coins[]
The primary currency used in Tadpole Pond, used to buy special items like group heals and accessories.
There is a tadpole in Tadpole Pond that lets you trade 200 coins for one Frog Coin and one Gold Bars for 20 Frog Coins.
You can also obtain Frog Coins from hidden chests and the following minigames:
Midas River Minigame
Minecart Minigame
Booster Hill Minigame
Sky Bridge Minigame
Sky Troopa Minigame
Frog Coin Shops[]
Mushroom Kingdom
Tadpole Pond
Moleville
Booster Tower
Seaside Town
Barrel Volcano
Factory
Galaxy Coins[]
New to Armageddon, Galaxy Coins are used in Star Hill to increase party members' levels or buy powerful items like Galaxy Apples and Manifest Illusions.
You can also go to Star Hill to trade 1000 coins for one Galaxy Coin, one Gold Bars for 5 Galaxy Coins, or 5 Frog Coins for one Galaxy Coin. Note that Gold Bars give the best deal!
You can also obtain Galaxy Coins that are floating in the overworld and from the following minigames:
Booster Hill Minigame
Goomba Thumping Minigame
Converting to Coins[]
Once Smithy has been beaten, you can convert Galaxy Coins to regular coins by talking to Rikku and buying Mighty Guards.
Each one costs 5 Galaxy Coins (5000 coins) and can be sold for 2500 coins. This may seem like a bad idea, but you can get Galaxy Coins much faster than thousands of regular coins!