Fight in the Pit to get various rewards, including gems that can be used to purchase Gold Chests for new heroes. Select weaker enemies that rank as high as possible and remain at the top long enough to win. Replay stages to collect Hero Stones. This will require some times, and will unlock heroes unlocked one by one. Start by tapping the hero you wish to unlock and view their information. You will be shown all methods to get their Hero Stones. Complete those stages until you get the desired Hero Stones. Watch the traders and complete their missions, as some heroes can only be obtained by doing so.