Great idea for letting player choose when to upgrade, a little nice risk-reward trade off. I think it has a potential to become very good if you keep working on that risk-reward level up system!
Also, perfect control feeling and great accessibility feature allowing controller support, However I couldn't get my Stadia Controller to work on your game, unsure why. (Stadia sometimes doe not work for certain games, not your fault :) )
Also, why casino? Interesting choice! I'd like to know :p