Posts in our company's page or on our own walls gave us the best clickthrough, and we did a lot of grinding to build up our audience there. Facebook ads did well also, we would pay about 30c/click and something like 10% of those turned into sales. Instagram actually didn't do well for us - we got a higher sales capture rate but fewer clicks. We just didn't give the insta account the attention that it deserved (before I left the business, anyway).