Though I don't really play in that part of the world too often, my suggestion would be not to declare independence anytime soon. Bad, bad idea. Even if you manage to gain independence, someone will try to eat you alive soon, so make sure you still have your big liege to protect you - at least until you feel like you can survive on your own.
Also, marriage. Marry. Marry your useless male relatives to female heirs - though you probably know that one already. More interesting is to marry your female relatives matrillineally to male heirs with daddy issues (basically, spend a lot of time on the lookout for male heirs to various empires, kingdoms, and duchies who hate their current lieges - invite them to your court, where you can matrillineanlly marry them to your female relatives). That way, once you establish your dynasty elsewhere, you'll have several allies by default.