Website can be a portal for your sucess. If your traffic on website is good then your customers are facing getting required data from your website. This could make them seek your competitors (word of mouth would change too) which can be dangerous for your business. To fix that, try Live Chat Support for Website, its effective in such cases.
If your traffic is reducing then you should work on publicity of the website. For that you can consult Google as it is the best serch engine. Search effective ways to promote website.
Hope your problem gets fixed soon.
With little to no budget, I suggest leaving business cards around instead of post cards. Business cards you can get for free from Vista.
If you know SEO, you can start it yourself with very targeted, long tail keywords. They will be easier for you to rank for in less time. Offer something on your site for free, such as an e-book related to the site. They have to put their email in to get the download link. Getting their email is very, very valuable for marketing.
Use Facebook and Pinterest!