I don't run a forum anymore. But when I did, I mostly used Phpbb. I have used Conforums and Suddenlaunch before and I was happy with the results.
I have always used free hosts, as I don't have the budget to constantly pay for a site.
1. Submitted it to as many search engines as I could.
2. Put the site link in my signatures on sites I am a member of.
3. Used Promotion Forums services to get them up and going.
4. Submitted my site to directories.
I usually don't get into buying posts for a site. Doing the Credits on the forum for them is great, but I usually don't get into real money stuff.
But I think Daisy is right, $1 for 77 posts is a good deal.