I'd advise you to go to Tale Worlds and read up on the single player campaign before you get too deep into it and mess up.
For instance, I didn't know that you could start your own kingdom before I already became a vassal for the Nord King, so I renounced my oath to him and really upset him. While I was under him, I raided towns and caravans of other kingdoms, so pretty much everybody hates me and my fledgling kingdom. Also, when peace is declared if your vassals are prisoners they are released but your companions aren't, you actually have to break them out of prison. I had an awesome engineer, doctor, military tactician, and logistics expert as companions, but I made peace and now they are sitting in a prison tower while my army remains expensive, slow, and ineffective.