Your civilization's Monarch is currently easy to attract and will be killed by experienced players as quickly as possible. If their demands for adamantine are not met, all your metalsmiths are imprisoned or killed, so at the moment there is no real sensible alternative.
It seems unrealistic that a young upstart colony such as yours could so quickly and bloodlessly become the capital of a Dwarvern civilization. The current system also raises further questions, when my capital gives a caravan tribute, I'm told that the King shall receive my offerings but it's probably just being embezzled by whichever despot is ruling over another fortress. These supposed vassel states pay me no tribute and their leaders are not accountable to me in any way. A short term approach to making the tribute feature more useful would be to make immigration dependent on payments made to the King, perhaps $500 per immigrant and a limit of 30 immigrants per year.
I want to run an empire and I want to feel like I've earned that empire. I know that none of the conquest features will be implemented for months or even years but I guess that it can't hurt to make suggestions. Perhaps your fortress could be given a lesser noble who you could use to either declare independence or claim the throne from the rightful King, igniting a Dwarvern civil war. In the first case you would need to fight off their sieges until they give up and recognise your status as an independent city-state.
In the latter case, one by one the other Dwarves could be brought into line, forced to pay you tribute and forced to provide soldiers for your campaigns. The dynamics of international relations could be very interesting. I was wondering why the Goblins had a human leader, maybe they'd been armed by humans as part of a proxy war and their military adviser had gone native like Kurtz in Apocalypse Now.
Moreover, I advise that Carthage *ahem*, sorry, Elfland must be destroyed.