You may need to spend some money to notice a difference which I know is hard in the early days but speculate to accumulate as they say...
@Lee Oakley does the SEO on our site and the hits on our site have doubled in the 12 months or so since he started. It took about 3-4 months to notice an improvement but since then it has gone up more or less every month since, as have the enquiries we receive.
He started by fixing some basic issues we had on the site and then found gaps in the market we could go after. You sound like you are prepared to do some of the work yourself which is great but I think if you are relying solely on facebook/twitter you are probably going to always struggle.
You could try amazon/ebay and put in some business cards in hope to direct those people to you in the longer term but you probably need to be looking at the bigger picture, which is scary when the smaller picture is not even paying the bills. As the saying goes, keep doing what you always do and you will keep getting what you always get - or whatever it is.