There are several types of resources:

1. Coins. Needed for training heroes.
2. Bucks. Premium currency. Can be used to replace other resources or save a series of victories.
3. Batteries. Needed to upgrade your hero abilities.

4. Nuts. Together with gear copies, they are used to increase a gear tier.

Resources can be obtained on the Path of Glory, as well as for levelling up and opening various chests.