Fun game! I'm interested to see where it goes. Some suggestions:
A larger diversity of upgrades. There's a large period of time where there's nothing to do towards the end of each section (especially the pink). Other people have suggested upgrades that modify multiplier chances and I completely agree.
The Combo section needs to be reworked. It feels very disjointed from the rest of the game.
You use "get" sometimes and "collect" other times. I think it'd be clearer to unify them to "collect".
The final blue upgrade references a pink square. Without knowing about the 2nd section of the game, I thought the pink squares were the later squares of the blue section and kept trying to collect thinking "is this pink? It looks pink". It's not known to the player during the first section that there are even other currencies besides square (no color specificity) and magic.
Small bugs:
Very rarely when magic rolls over an exact thousand it loses the decimal place for a frame then comes back causing a jitter.
Landscape mode on Android: the spellbook and combo/main selections push the resources offscreen, and you can't scroll to see them.