My landing page has an email capture form that I quickly change to match different offers. I need not only a low cost advertising channel, but quick execution (unlike adwords).
I'd set up Facebook ads because of their robust ad targeting platform so that you can laser focus your targeting which will keep your ad spend to a minimum. Then, I'd use those ads to drive traffic to different landing pages with different offers to see who's responding to what. Then, I'd have each of those landing pages integrated with a different email list in your email provider (aWeber, MailChimp, etc.). I prefer aWeber because I use a tool called AWProTools which offers a lot of features that aren't included in any of the other email platforms. Then, I'd set up autoresponder series in each of the email lists that are specific to whatever type of offer was being presented in each landing page. You can build out your entire sales funnel like this and then just let it run on autopilot.