I am travelling right now to your house to help you defend your fiefs. Here comes the watershed.
I mean, how else could I help you? I can aid you only with a few pieces of advice. Level up a bit and gather companions. Distribute their skill points with respect to their abilities and establish good relations with settlements you will draw troops from. Then, learn the rules of supply and demand and their application to the towns of Calradia. Earn a lot of money and then you are ready to recruit troops from villages, train them quickly and upgrade. Capture castles and towns and repeat until you have a solid foothold. Learn which castles and towns need siege towers to be built (first focus on ones which only need escalades with ladders, as they require less time to besiege). I have unified Calradia in unmodded vanilla Native with no cheats on highest difficulty levels and I can attest you will do well if you stick to this set of principles and pieces of advice.
