So I have a few questions:
1. Where do I get resources? Do I get them from killing troups?
a. If it is from killing troups does the enemy get resources magically? I sent everything I had at a fortress and killed all of their forces, but the enemy sent a HUGE wave after me. Where did they get resources?
2. Does the combat work like this: Arial beats Calvary, Calvary beats Ranged, Ranged Beats Arial?
The fact that map grew after beat in the first castle was unexpected! That was actually pretty cool, and if you could somehow capitalize on that. Perhaps make some sort of resource to be gathered? Not sure.
I think you should try to do your own sprites. It is really the best way to learn how is to try. Then again, you might be trying to sell this and not just create it as a LEARNING project.
Anyway, keep up the progress.