Just like it's been said, your income is so low and potions are so expensive, that you can't upgrade your heroes. All you can do is buy potions or your heroes will die. And if your heroes die, you don't get to hire one for a low price, your game is just over.
If the balance was fixed, it could be fun. But, the balance is completely broken, so it sucks.
I started, it looked interesting, but i quickly realized that there was no way to manually obtain gold, and i could not figure out how to disable an adventurer. i figured they'd just stop when they're on the verge of death. overall the main problem i have with this game is that there is no way to obtain gold manually which completely ruins the game.
You stop an adventurer by switching his green light to red or pressing the pause button on the side. It's also explained in the tutorial. Also please note this game isn't a clicker, it's more of a management type game.
Honestly loses out on every front, since you have to maintain a certain amount of money at all times because of the high cost of potions or hiring new heroes. It is extremely easy to just lose early because you only roll high cost heroes or a very greedy first hero during the tutorial. Try again at some point maybe, but as is it is not worth playing.