Gems are the premium currency, obtainable through in-app purchases, some Chests, and Quests. They can be used to speed up Chest unlocks, purchase Gold, buy Emotes, or enter Grand Challenges. The most efficient use of Gems for free-to-play players is typically entering Grand Challenges (if you're confident in your skill) or purchasing Emotes if you value customization. Avoid using Gems to speed up Chests, as it's generally not cost-effective.
