This isn't really true.
Diligent does help, but its decision only gives 0.2 development growth pr. month (before modifiers from the county).
The ghoul/revenant buildings doesn't have any development growth modifiers (at least in the public version I don't know about the dev build). There's one for hunters but those make for terrible vassals for a vampire, what with wanting to kill you and all.
The other big modifiers is that 1) there's a stewardship perk (third on the right from the top in the center tree) that gives monthly growth in your capital.
2) the duchy building prince of an X, gives development growth itself (starting at 0.1 and growing to 0.2) so upgrading that can speed things up a bit, but only once you have a significant development already.
3) Holy sites that doesn't have a special unique building allow you to build a normal grand temple/cathedral/mosque which gives a bit of dev growth. There's also a couple special buildings here or there that gives growth.
4)The road buildings for road of humanity or the ashirra faiths gives a bit of dev growth modifier at higher levels.
That's all the ways I'm aware off for speeding up development. It can be significant if you really focus on it, but it's still very slow, on the orders of decades or even centuries to get anywhere
Thanks a lot.
I've played only as England as vanilla CK3, and after a while currently playing PoD.
Started as Queen Petaniqua of Clan Baali. I am wondering where I should move to, as her starting area, kinda suck.
I could go for the kingdom of Nikaea, it has greek culture, it's on the middle of Byzantine Empire, a bunch of counties with 1 - 3 slots to build baronies, decent development, ok terrain, although I'd probably need to make some pikes.
I could take the Kingdom of Jaziba, it has 3 counties with special building adjacent to each other in the same duchy (but 2 seems to be bugged/can't build anything), the capital would be in a flooded terrain, Wall of Sacrifice gives up to +3 Knight and +30% strength, counties with 1 - 3 building slots.
kingdom of Mesapotamia. terrains are flooded. House of Wisdom and Imam Ali Mosque Special Buildings.
Thing is, Imam Ali Mosque has a requeriment of the True Faith consider it as an holy site. The Baali Religion doesn't, but I could later create a new holy order there (probably won't work though).
I need to head south of my starting location, due objectives and such. These seemed to be the best avaliable.