Gold: Earned primarily by clearing stages. Can also be purchased from the store. Mainly used for upgrading your heroes and buying some store items!
Diamonds: Can be earned from Quests, first time stage clears, the store, and more. Mainly used for making purchases in the store for chests, shards and refilling your energy.
Tower Tokens: Earned by clearing stages in the Towers (unlock at player level 10). They’re spent in the Tower tab of the store to purchase various items.
Clan Tokens: Earned by donating runes to your clan members when they request them. They’re spent in the Clan tab of the store to purchase various items.