Facebook is not a sellers network and will remain so for a very very long while. I believe the aim in using facebook is to engage and attract participation in some social activity rather than a sales pitch to user.
Think of some engagement action to your ad, you will have to encourage users to react with your ad propertiies such as making a statement and ask users to vote, like, watch a viral video, listen to a secret recording, get users to agree, disagree or answer a simple question to enter a competition .
Consider this example, you have a new blogpost, online or autoresponder course or ebook that teaches users how to upgrade their smartphones from a version 7 to a version 8 without the need to buy that new phone. Do you see the benefit you are offering here? Remember 70% of all internet users are using a smartphone to access the internet and yes you can upgrade your OS and Firmware to the new version for quite a number of Android Smartphones .
So, here you go, most smartphone users of particular brands would be interested in downloading this for free or even for a small fee. You now would have collected their email addresses, among other vital information about your users. You then further engage your new users by asking them to complete a small survey (this survey could very well be a CPA offer where you get paid when users complete a survey) asking pertinent information from which you can now determine what best to offer for sale to your new userbase.
Lesson learned : Upfront selling hardly ever works on social media as your primary aim is to get users to interact with you by offering something thats beneficial to the average user