like, we sell cheaper-their local manufactories can't keep up with our better/more goods, we "make" it so that they can only export non-processed goods (preferably mostly only to us). This would mean that all the rich ppl and nobles in said country are either afraid/controlled(puppet) by us, or simply their best option at getting richer, which means that we can influence the highclass i.e. their politics, which means we get a way of making them even more reliant on our stuff (food, drinks, clothes, weapons, good wood , mercenaries/soldiers, which even if not in a complete maner, would heavily stack our interests being theirs too, cause even just 10% of any basic/esential goods is a lot).
Basically, we try having them give an inch, and swiftly go in taking as much as possible. And since this is pretty much a deathworld, a lot of ppl wouldn't mind small things like slowly , and increasingly, let a foreign cult in their land for stuff like lots of guns etc..., or even just food if there's a famine .
That's just an example, we could otherwise force them to stay neutral in any fights we get into (or even have them help), get raw material like iron, 'n stuff, Maybe have them send those "troublesome" kids with magic potential?
idk, I only know WHF from the total war game and quests such as this .