You begin the game in the Proving Ground where there are three heroes (Stars) that you can unlock. These are the Barbarian, Ranger, and Huntress. Regardless of which one you choose it is important that you continuously upgrade them so that you are able to complete the levels and progress to Bronze where you will have the opportunity to unlock some different Stars.
The character you decide to use initially will ultimately depend on the type of play style you want to adopt, whether melee or ranged. You may want to consider the Ranger, this ranged hero is able to deal high damage at a single target from distance with her bow and although she is the weakest of the characters she can be particularly effective if you keep the Barbarian close by to attack anyone that tries to kill her.
Shoots arrows at one unit from range. Can also hit flying units.
Poison Arrows Buff - 2 Energy:
Applies poison to your Ranger's attacks.
Quick Fire Buff - 2 Energy:
Speeds up your Ranger's attacks for a short while.