One of the best low-cost ways to promote your site is to get other sites to link to yours. While it sounds simple, reciprocal linking can be a challenge.
Look for smaller sites that attract customers like yours. This works best if you aren’t in direct competition. Let the site owner know you have good information or resources that would help their customers make a decision to buy from them.
Suggest they link to your site using a new window that allows the customer to stay on the original site.
You can even go a step further by creating a special page to compliment the other site. Find out what kind of information the site’s customers would appreciate, then put that info on a page of your site.