Thanks for the reply Razorflame
I have been reading your guide and I restarted, currently back at lvl 10, army consists of:
Bowman, Alchemist, Horseman, Cannoneer and Evil Beholder
But I actually ran out of Horsemen some time ago, kinda cheating with those, haven't found a unit to replace them with.
Out of cannoneers as well now, need things to replace them with, managed to open the Creiston mines, but can't attack the castle yet.