What really did it for me on this game, was this little exploit I found which allowed me to pay for another die's upgrade, using a different pool of resources just by stacking a different die over an already occupied slot. That little bug was really insidious, but as they say:
"It's not a bug, it's a feature!" Hahahaha.
This was really fun.
Quite confusing in the beginning, as indeed the learning curve *is* steep. But once you're past the initial hurdle, it becomes plenty entertaining.