The best way is following accounts/blogs in your niche, I am sure many tumblers will follow you back if your blog content is good. You type in „big breasts“ into the Tumblr search and then click on notes and follow followers of other blogs in your niche. They will not follow you and they won’t click on your links if you spam them with posts like "Reblog my posts" et cetera. It takes some time to build up followers, but the benefits far outweigh having a fake high follower count simply to look cool or massage ones ego. And there are really only 2 rules of interacting, don't be an asshat, and don't whine/beg.
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