There was a novel that's completed which I really loved... it MIGHT be called city of sin? I might be misremembering though.
But it was about one powerful world (the MC being a son of a smallish noble) who would monopolise rifts into other worlds/planes where they would trade/conquer/explore/develop worlds, extracting resources and trading / battling in the main world for position with the other nobles.
It was years ago but I really enjoyed it and it was heavily about developing, I think he enters his first sub-world thing with a handful of people and builds it into a nation with armies and so forth.