Really love the theme and premise of this game! It seemed like a lot of the nuance was in figuring out which combinations of various skill levels could achieve the same likelihood of success for the lowest price. After a while, it felt like my gold was probably going to grow more-or-less unbounded and my only real constraint was the availability of adventurers. Echoing some of the others in this thread: it did feel a bit repetitive after a while. I think this could be remedied by going in one of two directions:
1) Make the adventurers persistent in a way where you can level up their skill while keeping their costs down. This makes the individual successes/failures of a group matter a bit more since there is a long-term goal of getting you cast of regulars leveled.
2) Squish the individual adventurers down to just total numbers of adventurers available at each tier. This eases the friction of having to scroll down an ever-growing list of adventurers to find the letter grades you're looking for.
Otherwise, the control and flow of the core gameplay loop felt solid. Great job!