Fun game. I'd argue you didn't even need to Balatrify it with a quota to meet to win the level and gambling, it's fun to just drop the marbles and see if yours wins. Making it a "career" mode and a "free" mode for people that just want to see it go could be fun, and I can also see it having a "multiplayer" where you get to name multiple marbles and see if yours or your friend's wins. Sometimes I spin a wheel to make a choice for something trivial, and that feature could also work for that.
I like the gravity power-ups, but hard to see how it affects my moves, so I think you could be a little more exaggerated with it (and while I can understand what you were going for, it being a passive rather than a trigger on a cooldown probably would be better).
Where I see the most potential is how much you can do with the level design. You could go full Sonic level and theres tunnels in the walls, bouncy springs, loops and ferris wheels; make the marbles journey an odyssey that's thrilling to watch passively, and some areas/shortcuts that can be acessible through power ups that change your features (consider how sonic riders had the Power Flight and Speed types of racers, that could each get on a special track unique to each), and it'll become a spectacle by itself, and create in players the desire to spec builds to see where they can enter or not in certain stages.