Rewards are given to players in the form of coins & experience when they die or when the minigame ends, with the winner receiving gems in addition. Leaving mid-game cancels out receiving rewards.
Coins can also be earned by completing dailies, and gems can also be earned by ranking or levelling up. Additionally, both coins and gems can be acquired by redeeming vouchers.
In Royale, combined rewards are only received after getting eliminated, or winning the entire batch.