For aged niche, relevant domains or done for you affiliate sites check out ODYS. Global: https://odys.cc/ Use this link to grab your free $100 bonus just for signing up.
When doing SEO you want to make sure you use the title tag, the URL and the header tags on your page to make sure that you target your best keywords. Doing on-page SEO does involve targeting your keywords after you do research and make sure those are featured prominently on your page including in the title, URL and headers.
Find out more in this video how I would personally have this laid out.