Hero Tokens
Visible on the stage select screen of the current map is the hero token you may obtain through completing the stage or using the Quick Loot feature. The type of chest that you obtain at the end of the stage determines your rewards. In terms of Hero Tokens, the silver chest gives one token, the gold chest gives two, and the Ancient chest that is rare gives three hero tokens. If you are close to obtaining the hero tokens you need, you may opt to refresh the availability of the token for 20 gems since you can only obtain a token from that stage once a day. Do note though that succeeding refreshes will increase in gem cost.
Star Rank
The one to three star rank is the indicator on how well you did in a stage. The only requirement for three stars is that none of your heroes die. Three starring a stage unlocks the ability to do a Quick Loot run of the stage. Sneaking past all the enemies and straight to the end chest. This action requires Loot keys that can be obtained from sparkling objects in the background, chests, rewards, and quest rewards. Loot keys can also be bought in the various shops in the game.
Sparkling objects
Scattered around each stage are objects you can tap to inspect. Sometimes, these objects have a sparkling effect around them. Inspecting them when they have this sparkle always gives rewards. The rewards you get are random. You can get gold, loot keys, or a few points of stamina, or a combination of the rewards. Keep your eyes peeled for them.