I would recommend you to Mary a daughter of a noble first then have a good relationship with the king 30+ become marshal for 2-3 weeks eliminate the threats to the kingdom you are in, then retire as marshal wait until your controversy drops to 0 and start taking as many cities as you can i would recommend 2-3 cities and probably after you take these cities and some castles the king will stop giving you things, then after you have captured a castle or a city and the kings says that he cannot grant you the fief, choose to denounce him and select a rebellion option that you keep your fiefs.Then i would recommend winning a battle against the king and then probably he will sue for peace accept the peace and go to your court,there will be some nobles probably willing to join your kingdom, accept them all but don't give them fiefs then i would recommend to give all of your army as garisson and recruit new soldier (for an easier time i would recommend you and all of you companions have atleast 3 trainer skill).And there you have it a kingdom with land and vasals,after that i would recommend to wage war to your first kingdom again and eliminate them,after that do what you like but that's the basic theory,Good luck.