Both work is most important for seo work. But off page most important means 65% & on page is most important means 35%.
some small description for on page & off page.
On-page SEO are focusing on the on-page elements, such as Unique title tags, H1s/headlines, Copywriting, Adding descriptions to images, Crawlable links and Internal navigation while Off-site SEO, focuses on things beyond your website, such as Press releases, Link building, Advertising and Social media.