While Brave Frontier's Arena Orbs refresh steadily each hour, you might want to speed up your progress through the Arena ranks. In this case you can use a gem to refresh your Arena Orbs to full.
To refresh your Arena Orbs you can simply do any of the following:
1. Continue on to another arena match when your orbs are empty. You will be asked if you want to refresh your orbs with a gem or;
Previously you can refresh your Arena Orbs in the Shop Menu. However, this feature was changed in order to put in new features for the game. Check out the features in the shop in the game to know more.