Personally I think filling out the vanilla some of the subs would be good to help drive traffic, which in turn helps determine which of the more niche ideas are wanted. That’s why I made !porninfifteenseconds@lemmynsfw.com. Some other broad ones could be general nsfw, nsfw_gifs, (is gonewild still a thing?), and maybe a rule34 com.
Go real vanilla. Romantic porn, healthy porn and so on. The main drive of the site is it's communities so it's better to fill in niches where people like to talk about the content than just another still gallery of semi-naked conventionally attractive white girls.
Also porn for women. The gals at Reddit built themselves really cool communities and I don't think there are that many corners on the internet where women can share and talk porn. Although this definitely needs to be initiated and moderated by women so if you're male not much you (or I) can do.
Agreed, probably would be better if there were a diverse set of main communities for users to start off on. A women-centric jumping off point would be great, but as a dude I can't really do much about it.