I adored this so much. It reminded me of reading the Redwall books I read as a kid. I didn't screencap my build, but I got very lucky and found a way to generate mana and use the wand that only required mana (no energy). I was able to beat the final boss on my first playthrough(!). Although my build was so strong that endless mode didn't feel that interesting.
My only immediate suggestion is that perhaps gold and mana could be stored separately outside of the main bag in some separate GUI? I understand for story purposes you're storing everything in your bag, but it felt weird for two almost-essential elements to have them be optional.
Either way, this game was fantastic and it feels like you probably already have an idea on how to continue to improve and balance it. Keep up the good work!