Coins are the most easily accessible currency in game.
How to get them Edit
You can earn them by completing tasks, plundering other players, fighting Boss Dragon and Acnologia, harvesting at your farm, and selling or pulling apart cards/equipment.
What are they used for? Edit
Coins are used to perform upgrades to character cards, equipment, or stat bonuses in your guild.
They can also be used to buy certain things from the Magic Shops and Black Store.