While “like” campaigns are out of style, having likes on your page gives you some organic audience if they are interacting with your posts.
You already know these people are interested in whatever you are posting about, so they are likely to be interested in further posts too.
There is the Chrome plugin that can automate the process for you. I’ve used it and it works well.
Except for the work involved, these are essentially free likes.
If you find a post that is getting a lot of likes and you decide you want more, you can run an engagement campaign with that post ID.
Basically you are “farming” your own likes as well as getting engagement on your post and possibly clicks or conversions.
For smaller budgets, I like using friends of friends targeting because you have double social proof on an ad. You have the likes, comments and shares. You also have the Your friend John Smith likes this …
Which is super valuable and gets people to pay attention.