Currently as it stands all the land on the starting continent is owned by the preexisting kingdoms. There is no land available to create your own kingdom on the starting continent.
You will have to either work your way up the ranks to become king, or work your way up the ranks to duke and break off as your own kingdom with a few other fellow dukes.
On the main continent anyways, the only other way is to travel across the sea and claim an area that hopefully accepts it or is unpopulated and create your own kingdom.
Either way I do wish you luck, however for recruitment the sections labeled specifically for domains for each server would be the place to post in your respected server locked area.