Facebook Ads Question (Help Please)

I've read the article about personal engagement in Facebook, after user failed to buy or visited with NO ACTION my website.

Please give me idea if it possible or not. I install the pixel.
I have for example different groups of users.
1) who bought something
2) who was with no action
3) who signed for free trial but didn't care about
etc.

Can I show personal ads to that users? I mean what is minimum group size to show them remarketing in Facebook?
Can it be for 1 user only or it should be minimum ten for example?

Really nobody can help???

What are you trying to achieve?