The first thing you should do is to see if the keywords for your google ads are so relevant to your business. It's better to target very relevant keyword phrases and to have a bigger chance to convert then having lots of traffic.
After that I think you should invest in a web marketing campaign. All the SEO in the world will not help you if you don't constantly produce new good content. Another thing, after you build your content, would be to market your business : spread the word on forums, blog related, social sites, social bookmarking, article writing websites. All this will get you in time better organic rankings and you could target many other keywords.
Maintaining a business blog would help a lot and even if you don't wanna write your own articles you can get very good articles for 25$ up to 50$ per article. If I would make a decision I would invest in blogging rather then PPC because with blogging, even thou the results come in time, you establish yourself in the market and you enhance the Internet exposure with a good solid base.