Refreshing existing content usually delivers quicker SEO gains, especially if the pages already have some rankings. Just curious, is your site already approved for AdSense? If it is, would you be open to discussing a potential partnership? Feel free to send me a message.
Both are important. You cannot ignore either. If your time is more important, you can hire someone for this work.
I generally start by checking my Google Search Console before taking any action. The pages that are getting impressions but are not moving will give me the best ROI when updated, and the pages which are compeletely dead will require more of a content perspective rather than just an update perspective.
