SEO Catchment page / Blog Pages

Hey Team, For product sales, what's the must haves for creating these pages. Good content, links to products, (how many links should I do per blog max?) should I be linking the keywords I want to be picked up for to product page. Should I write blogs on the same site as my ecommerce store or write them on a external website? Should I register a domain with the key search words in it to write the blog posts on? What other tricks should I be making sure I am doing to rank for these search terms? I have had a ecommerce store for 14 years but never done any SEO work, however I have watched my competitors sales skyrocket while mine stays the same over time even though I am selling a better product for a cheaper price . Please help!