Upgrade your hero throughout the course of the match in order to help your team topple the enemy tower (A gigantic Roadhog!) As this "RPG" is team-based, all types of hero activity are rewarded with gold! Damage, healing, shielding, etc.
Alongside gold, you will be spending upgrade points, or UP, in the shop. Each player begins with 500. UP is what allows the player to buy upgrades for their hero. When one runs out of them, they can no longer upgrade. Each purchase costs UP, typically 1, though certain upgrades may cost more of it than others. UP encourages build specialization and prevents infinitely upgrading titans from dominating the server.
All the typical stat upgrades can be found in the shop, and so too can special ability upgrades and upgrades for the tower itself (as well as the tower's pool of money, which can be taken from).
A communal bank for each team is also located within the shop. Take gold as needed or deposit gold to strengthen your team.