I have a solo girl blog that features all different kinds of solo girls on the root:
Solo Girl Daily
As you can see I then have links to niche specific blogs "Asian Sologirls" "Big Boob Sologirls" etc etc.....in folders so I can move the traffic around to try and give them exactly what they are looking for and build one big site.
If I understand correctly adding a few back links a week, say one to the root, and one to the boobs blog, and one to Asians blog, will all give weight to the entire site and not just the blog in the folder?