I've run many profitable campaigns on Facebook -- by not buying likes or advertising a Facebook Page. You can advertise normal links on Facebook and that operates like any other online ad -- some text and a picture, linked to a landing page for your own site.

There's no "likes" to count or "engagement" to measure other than the normal conversion metrics -- how many of the clickthroughs completed whatever action you wanted them to complete on the landing page, how many eventually convert to paying customers, and is their LTV higher than their CPA.

Facebook's also a great channel for retargeting. I run a campaign for Improvely there and the ads only appear to people that have already hit the signup page within the past few days.