As you get comfortable with online advertising, consider spending some of your marketing budget on set-price ads.
Do you subscribe to industry newsletters or regularly read blogs or other sites related to your business? Your target customers might, too. Advertising on web sites directly related to your business can be expensive, but with careful research, you may discover inexpensive and effective opportunities for targeted advertising.
For the best bet, seek out industry-specific sites and smaller online publishers. Few small businesses can afford an ad on the New York Times web site, for example, but a small publishing company might easily afford an ad in an editors' newsletter or community web site. A shop selling recording equipment might have great success advertising on a popular local music blog.
When you have identified a few sites that might cater to your target customer, contact the site publisher directly for more information about rates and the types of ads available.