How do i do a content gap analysis properly?

The order that's worked for me: 1. Pick three competitors who rank for what you want, not just the biggest names in the space. 2. Put them in a keyword gap tool and filter to terms they rank for and you don't. 3. Throw out anything off-topic or with no buying intent. This is where most of the list goes. 4. Group what's left by topic, so ten variants become one page idea. 5. Check Search Console for queries you already show up on but rank badly for. Those are usually quicker wins than brand new pages. On your own I'd cap it at ten page ideas, write them, then do it again in a few months. A list of 400 just sits there.