There's a LOT packed into this jam entry, you should feel proud! I played on normal difficulty and I did feel like I ran into some bugs (all the boss did was defend), but it was a fun experience overall!
You picked a tough genre to balance and mixed in procedural generation to boot; I think the biggest issue is somewhere at the intersection of these. E.g. how rare a particular material is vs what kind of skills it gives me access to vs the return on investment on the cost to use those skills in battle. Because of these imbalances I was gravitating to only 2 or 3 of the many available skills to get the most bang for my buck, and likely missed a bunch of cool stuff.
I liked the graphics in general, and the VFX in particular.
Impressive effort for a solo project! Keep it up :)