If you're creating content that isn't getting links you need to make better content.
The blog/forum comments and such like aren't just to get links, they're to make people aware that your stuff exists and if it's any good, hope that they continue to read your stuff and link back editorially. Guest post, network, get out there, but you're not going to be able to get a tool or outsource that. Accept that promotion is part of being a content producer. There's no shortcuts.
Realistically there's not much you can do with $200 (per month?) in terms of pure link building. Unless you're happy to outsource to people from poor(er) countries to do this commenting etc for you (and as it's tied back to you I wouldn't overly recommend it). So, you need to think a bit differently to attract links.
You could run competitions on your site and use that as prize money, you could give away stickers to likers or commenters, you could become a app dev and publish a free (to make and dl) iphone app, you could do any number of things to pull people to the site but you're not really going to get somebody to run a link building campaign for you at that price (I wouldn't imagine)
I don't really know what kind of site you run so can't give specifics.