You buy heroes from a shop for a specific cost (stronger and rarer heroes cost more gold). To build a great army, you need good gold management. This means that to place high or win a game, you need a good sense of the macro strategy in Underlords, not just the hero combinations.

You can use your gold for three things:

To buy heroes, which costs between 1 and 5 gold depending on the rarity of the hero. To re-roll the shop (refresh the heroes inside instantly), which costs 2 gold. This helps you find the exact heroes you need for your upgrades and synergies. To purchase experience. This helps you increase your level faster (you win a little XP every round for free).

Experience: Experience helps you increase your level, which allows you to include more heroes in your army. For example, in the UI screenshot above, 9/9 signifies that there are 9 heroes on the board. This is the maximum possible number for the current level of the player (level 9). Level 10 is the maximum level.

Your level also gives you a higher chance to find rarer heroes in the shop. For example, on lvl1 you can find only common (1-cost) heroes. You can find 5-cost heroes only once you reach lvl8, and the chance increases with higher levels.

Gold: You get gold from a couple of sources. First, you get a set amount of gold each round. Moreover, you get 1g if you win the round against your opponent, 0 if you lose it.

There are, however, other more strategically interesting income sources: