A couple of years ago my ecommerce site was in a similar situation - an average of eight visitors a day. It had sales pages but no extra content. I read loads about how creating free content on your topic and getting these pages listed in directories that don't allow commercial content, would boost my traffic.
At the time I think the 'provide free content' model was very fashionable. I did this and and did create astonishing results, going up to 50 - 100 visitors a day very very quickly, however, this was a couple of years ago.
While I was doing this I noticed that my title and meta tags were pretty nonexistant. I discovered keyword analysis and vastly improved my titles, meta data, and content.
A few months later I went on a dreamweaver course and moved my site from Frontpage Xpress to dreamweaver. The week I did this I bounced to again to about 200 visitors a day. When I say bounced I mean, the day after I released my new site.
A few weeks later I had some press coverage and got my highest ever day
Soon after that came my busiest time of the year and visitors climbed to 300 or over a day, interestingly though now is my busy time I've had no slacking off of visitors throughout this year, though sales have of course fallen.
I've begun to issue a newsletter and put it up on my web site. Interestingly my newsletter, which is often about quite obscure products, often ranks number three on google for keywords that won't get a lot of traffic, but they do bring in some.
I think poeple can sometimes focus on what google is doing to them when it might better to focus on visitors, your site could be on display all over the web but if your descrition doesn't entice people to click then you won't get any visitors no matter how high you are on google.
The extra content model really worked for me.
I was interested about your links from casino sites. Is this the area you are in? I am in an adjacent niche and constantly have offers to link to casino sites. I always say no.