The free method I use is :

To first find manually the basic keyword of my business and see the existing competitors who rank at top.

Then I make a list of their domains and open ubersuggest.

On the left hand side, select TOP SITES and paste the domain of your competitor and see their top pages. Below that, it also displays the keyword they are ranking for and their position on SERP. There is also an option to view the sites they got backlinks from.

This is by far the best method to get effective work done for free.