This is something that I just tried, and it worked for me. I'm not promising this will work for you, or if you'll want to do it or not but hey why not, it's free. I posted on my Facebook (I'm an event photographer so I have a lot of 16-20 y/o's as friends, I'm 17) "Any Tumblr crazed teenage girls wanna help out with -Niche site-" and got three people that know tumblr like the back of there hands to actively post and work on that account. I did the same method with the Facebook page, the blog, and the Twitter for this niche and I'm getting 300 views a day for a site that was launched 4 days ago. I also have three active article writers that write for the blog for free, and a graphic designer that I got for free. Enjoy the free assistance.