Cool Idea. I agree with Grumpy that the song is....a lot haha.
But I love the visuals, Nice level design. Most of my suggestions would be about tweaking the difficulty in various ways.
From an approachability perspective though, I have two suggestions, a little description of what each minion type is good/bad at might help. I just used goblins mostly. They seemed effective haha.
And some kind of visual marker for 'Max Gold' would be useful. but I LOVED the mechanic of the gold piling up at the corners of the screen. Very nice touch..
I really enjoyed it. Thanks!