Interesting idea to mix deck building with gamba,
Although I feel like the encounters go on for far too long. Maybe if kills grant you another spin to incentivize killing and speeding up encounters (might already do this but if so, there is not enough feedback that kills reward you in this way) Also getting an physical attacking move that requires mana but not having enough for it felt very bad and didn’t help with the very slow pace. If you wanna keep mana perhaps having a reduced damage/effect if you don’t have the required mana?
That being said a faster paced version of this is something I could see being very fun and engaging for multiple levels and be worth exploring further if it’s something your interested in working on more! Also would be cool to see AOE attacks or something like a lighting spell the can chain off multiple enemies!!