How to get backlinks

I have a travel blog and when i post a new blog post i use a link swap group on facebook but only get like 1 or 3 link backs.

But not getting any more as the blogs with higher DA score get more link backs in the group.

I am looking for a way to get more link backs and is a link back to your keywords in the post good or bad.

Also would like to know how do you know what is a good and bad link to link to on yoir blog post and how many internal and external links should you add to your blog posts.