Someone talk me through increasing organic keywords?

Easiest win first. In Search Console, filter queries to ones where you sit around position 8 to 20 and still get impressions. Google already thinks you're relevant for those, you're just not good enough yet. Add a section to the page that answers that exact query properly and the page usually starts picking up a bunch of related terms too. After that it's new pages. Group the leftover queries by topic and give each group its own page instead of stuffing them into one.