Need Facebook ad campaign advice

Hi, I'm looking to create a Facebook ad campaign for my startup, and was wondering if anyone might be able to give some pointers? I want to target users who either work at and/or like a specific brand/page. What would be the benefit if we do 1 campaign targeting all of the pages we care about, vs separate campaigns for each? I think with the latter, we could tweak our ad to be super niche. But wondering in terms of eyeballs/reach/cost, is there a difference? If anyone has experience and available for paid consultations, that would be awesome too!