I liked it :) I do feel like the placement of the UI is a bit off. I have to look back and forth between the top of the screen to see my gold, then back down to click, then in the middle, then up, down, middle in this endless loop.
A bit tiring. If it's by design so it's not too "easy" I can understand, but when difficulty comes from "hard to interact" for me there's a problem.
I would try putting the buying buttons on top, under the gold info. Or make those buttons bigger and also the difference between *can buy* and *cannot buy * more obvious, I think the colors are too similar between the two states.
When the battles intensifies I've been clicking a lot on buying buttons thinking they were in a *can buy* state when they were not.
Imo if you can fix those UX issues, that's a very good game!