I have a personal Facebook account that I use occasionally, but nowhere near as much as I did 5 years ago, instead of following family and friends now, it's mostly Facebook groups and I don't like the layout after the recent update. I also have a Facebook page that I use to help promote my YouTube videos but I haven't put much on there in months, now that things are picking up again I will try and be more active on there. I think a page is better than an account because people follow a page if they like the content, rather than a personal account where your friends may not care about your YouTube channel.
Last year I spent £3 on Facebook ads promoting my latest video over 3 days (£1 per day). It was useful being able to target quite specific people - mainly those who like the Facebook page of the place I was visiting - and I got quite a few hits from those ads and it cost less than a cup of coffee. I would do ads again, probably just £1 a day for a few days, but not more than I could afford to lose.