Well, the biggest thing that hit me is the lack of detail, that a thing you will have to work much with. Its all empty and with nothing to contrast it. Thats the terrain, with the gameplay i see two things. 1 is the drop from monsters. You should do so they drop random items, instead of the drake drop 1 Tiny Great Hall everytime. The other thing is, that there are several water ways, aka where you go down into the river, make sure they have the same size, the small ones are alot easier to defend, and you can cheat AI with it.
I have to give it a 3/10, its playable, but lacks terrain detail and drop.
If i shal give you a good hint, try to make some terrain maps only, get a feeling of what its like to make a map beutiful.