In my oppinion you should get your army together and rush the AI, because disbanding units will throw you back really hard. Mass recruit Archers with 0 Upkeep. I was able to get two expanding armys.
In my campain I prefered to move south/west because there you can wipe out the AI armys with nearly 0 own losses later. Ignore the moving rebels if you don´t have to fight them and NEVER attack them yourself. Let them attack you!!! This way they often won´t even shoot and run straight to you for Melee. If your army is up a Hill, it is really funny to wath them do their job.