How to gain tumblr followers?

hi, recently I've made a new tumblr and I only have 12 followers. 9 of them came from a follower app (which I don't want to keep doing because they're all fake and pointless) , and the others are my friends that I've asked to follow me.
I post a lot of my own content (with loads of tags) as well as reblogging other peoples'. I used to do this for ages on my old tumblr, and still had less than 20.
I've tried liking loads of photos on hashtags and following random people, but still no followers. I do have a blog, but I don't have any fancy cursors or anything because I do all of it on my iPhone.
please help me gain followers!
my tumblr is spacekid1995.tumblr.com

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