My personal opinion (though not based on any experience) is you should not rely on 3^rd party massive advertising services to do this job for you. The general formula is you get 20 social media exposures for every dollar you spend. However, there’s no way to track this. There’s no accountability for the 3^rd party service and there’s no guarantee that flashing and Ad on a sidebar or a banner will lead to a sale. By working through your own personal and professional networks, you can expect a much more genuine and robust response rate; you’ll be able to track the progress of your efforts.