keywords position

I am golang developer and for learning purposes I want to create small system to track the rankings of my website for some specific keywords. I want my program to get keywords rankings on a daily basis. What is the best solution? I tried just to scrap google search results. It works using...

Keywords are to be used throughout the site to get listed in search engine results or only on homepage would work ?

Listing of keywords only on homepage is suffice or the keywords should be used throughout the site on each page like page , title , heading etc.