Honestly, I've never bought links for any of my forums or sites. If I was "serious" in them, I probably would advertise on bigger hosting forums, such as HD here.

I mostly advertisted by my sig and/or through emails. I was able to buy a email database from someone on a forum and was able to sent out many emails.

BTW, how are your advertising techniques working out? Did you get a lot of traffic from spending that $300?