Base concept is interesting. Seen a few build your die games in the past but they were always turned based so it was novel to see it applied elsewhere. The die faces pricing felt a bit limiting. I think a rebalance around that would do wonders. Elemental die faces have potential if switching the die I'm using on the fly. I think changing it so the die face facing the player is the damage would make the dice feel more intuitive for how much damage I just rolled. And making everything faster pace. You have the beginnings of what could be interesting Metroidvania material.