I like this game a lot! The art style is clean and appealing, the theming is fun, and I was surprised by the buffs and debuffs you can get from the slot machine. When my screen started wobbling I had the biggest smile. The "90% of gamblers..." game over screen got a good laugh out of me too.
The biggest thing I think you can take into your next jam is this: Sounds are the most bang for your buck you can get when it comes to game feel. If you can only implement one piece of polish, make it a sound effect each time the player gives an input. This will be a huge benefit during the design process and helps you find the fun.
I can see in a comment below you mentioned that you wanted to get to sound implementation but ran out of time. A fantastic method I'm hoping you'll try is start your project and add some generic placeholder sounds you have the rights to use They don't need to fit great and it's actually probably a good thing if they don't so you don't forget to replace them later. When you implement a feature, for example the damage numbers or rolling a slot machine, add the sound implementation right there with a generic sound effect. Now that part of the game has sound implemented and it's easy to go back and replace the effect later with something more appropriate. Even if you end up not having time to go back and replace the placeholder sound, a generic sound is usually better than no sound at all. If you leave sound until the end, it's hard to get back and do a good job. If you bake it in along the way your game feel is gonna skyrocket.
Fantastic job, I can't wait to see more from you!