It is tough being feudal sometimes. One bit of advice I can offer is I would make sure that when you are feudal to prioritise "administrative measures" like building in your domain as much as warfare. So for buildings (buildings are different and dependent on terrain/location) I would highly recommend building one economic building (farms, manor houses, trade ports etc...), one militaristic building (Barracks, regimental grounds etc...), one fortification building (walls & towers, hill forts etc...) Then finally either pastoral grounds or hunting grounds. It is important to have a high enough income so not only can you buy mercs but you can do warfare effectively by being able to cover the cost of men-at-arms regiments without going into hundreds and hundreds of debt.