i tried locating your tumblr blog but it comes up as not avail.
i got a tumblr blog as well for nfsw, its a tranny/shemale one, got about 780 followers which i consider smallish atm even for a niche related blog. Ive seen gay blogs on tumblr with over 12.5k of followers, so the 380 you got is in all fairness nothing big at all. Try not to post 100 pictures you randomly collect on google image search but go into your affiliate accounts and get the best of the best picas to post.
Good tip for getting more followers is to not only post one image posts but also compose some posts with 3-7 pics. These get more reblogs and followers then the one posts wonders.
just my 2cents.