Added the follow bot as an attachment.
Open config.ini and fill in your email/password, then to run, I run on my server, so to run the url would be:
url/?link=tumbler-permalink
The tumblr permalink is the source of the post, the orginal poster, not the re-blogger.
I am by no means nor do I consider myself great php coder (I'm sure someone could make something way better), but I ran this script to get me 109,000, 38,000, 10,000 (3 times) followers on individuals accounts before tumblr implemented the follow limit.
You can only follow a maximum of 200 accounts per day, and make a maximum of 200 post a day. Since you guys are not concern with following a lot you should receive followers and not lose them for unfollowing. When I had 109,000 I lose about 1,000 when I un-follow them all. There is a follow limit of 2000 though, so once you hit that mark I suggest you imacro un-follow them, only takes a couple of minutes.
Try to find post which are relatively new, so that the people it follows are online/active, I usually ran this on the radar since radar updates daily, and gets tons of reblogs, I assuming y'all will be focused on post from your niche though.
Let the script run once through the page, it will refresh to continue to the next page (when tumblr had no follow limit, a post with 1000 notes would be around 1000 new followers), but don't allow it and just find a new permalink. Just trust me on this part.
After you follow them all and are finish with your own post. I also suggest saxgod's amazing reblog bot (search Tumblr Reblog Bot v0.6), so that you will actively reblog and like people post (tumblr people love getting reblog & liked), hence more followers when you can't follow more..
Also try to have a neat theme, and a good first page of post that people will see on their first impression, having your first page full of crappy post will not help you, just hurt.