Just try win battles whit your king and try make war against factions. One Easy way to get influence is to help ally. For instance when playing whit Danes help English armys against France. If you take out Germans they will really need it. This is again one reason why navy is important.And always remember to have good agents ...You can kill unwanted heirs. I Once got 4star Heir to my 4star King After that I started using my new heir in battles and when he was made to king he was 7star king and same amount influence.
Acumen and dread can be harvested whit assassins "Sometimes".


Rebellions can be your friend=).