ontrary to what marketer believe, Facebook page wouldn’t help you if you don’t have the customer first. People come to the page not because the page in facebook exist, but because they already like your product. The mere act of liking a brand does not affect a customer’s behavior or increase purchasing. Nor does it spur purchasing by friend.
So how to know when you start to advertise then?
Get a metric across the whole product and validate your assumption by experimenting in 9-10 different content type in 2-3 months. If something seems like a good hit, you can start advertise, and then validate the result against the metric again.