I'm kind of in the same position as you - just starting out, with a blog in a very certain aspect of sort of a niche topic. But I've built traffic to other projects before and I think wordpress.com will work much the same way... I'm already starting to see some views, which at this stage in the game is exciting to me.
I always think of it as building blocks. Everyday I try to put on a small block. That could be commenting on another blog, participating in a discussion on a forum, ect. Then there are other "bigger blocks" you can put on somedays - if there's any one you can sort of collaborate with.. like in your case, if you could do an interview with someone who has a well known blog related to manga, or maybe an artist in a similar style? Use someone who already has somewhat of a following and will link to your article.
Also, I don't believe in stiring up drama just for traffic, but if there is a topic related to your blog that people have strong feelings about, that you have a very decided opinion about, participating in debates about that on other blogs, or even on nonwordpress sites (if you are linking to your blog from your user name) can really give you a boost. People want to know about people who they feel are their allies in a debate or people who they vehemently disagree with.
I know when I was doing a videogame related site, debating anything related to gender stereotypes in games or gaming would give me a boost if I participated in a debate on it. Because I happened to have a unique pov on the topic that didn't fall under either of the usual stances, and I could articulate it well.
That's my two cents, its not the most expert advice, but that is what I have been doing that has helped me start building from the ground up.