[Beginner] Few questions about social networks

(Sorry for my english , not my native language)

I was never too much in the social networks sites before like facebook/twitter/instagram etc so I'm not sure how it works ...

1 ) I was wondering - if I want to get some traffic through those, how do I get my first expose"?
Who will see my posts if I don't have any followers at start? Do I need to generate them , or make real followers?

2) Either I have followers or not, how should my first posts look like? (for affiliate for example), do I need to write something and link my reference url? and how often?

3)Should my account be on just one specific niche ? or just anything I would like to post?

Can anyone share profile for example?

Thanks

you can have a lot of traffic if people like your post and re share it , so try to make attractive content to the audience

I have same questions, whst about content And pictures for your niche? Is IT ok to steal content from others or Google?