I have 133 fully upgraded (I bought all the equipment upgrades) muscovite cavalry mercs. I have defeated armies of twice my number on the open field.
I don't know why anyone buys marksmen of any kind. They are almost worthless. My cavalry with full armor and steel shields can take at least one bullet without dying. I also have a doctor with 8 of each medical skill (Academy helped), so even if I lose 10 guys in a fight, 8 are wounded. The only thing that slows down my cavalry are pikemen, but I gave my cavalry the best guns that they CAN fire from horseback, so they just ride circles around the pikemen and shoot them.
My cavalry cost $1500 each to hire, but I have over a million $ from trade collecting interest. So that's $200,000 per month coming in from my interest alone. Money is not a problem. I have a garrison of 500 in a super rich town and I am my own faction at this point.
If someone goes to war with me I just pay them off with my hordes of money and keep trading.
Everyone on here is always talking about the weaknesses of cavalry, and they are forming long thin lines with their marksmen.... I blow through lines like that all day long with my cavalry. I use a bow because I can fire 3x faster and when defending a castle I get nothing but headshots, so one hit kills anyway and I can carry much more arrows than bullets, and fire faster, and I can pick up arrows that get stuck in the walls of my castle. So I arrive with 89 arrows, use those, then pick up the arrows the enemy shot at me and keep going.
The only thing I haven't figured out is how to recruit lords to my side. I hate doing those stupid little quests. I should be able to buy them or promote my companions to lords.
I guess I'll just have to leave 500 troop garrisons in each of my towns to make sure they don't fall when I'm not around.