The idea behind on page and off page optimisation is to be consistent with your targeted keywords
Site Speed and SEO Best Practices
Google has shown that site speed is one of the signals used by its algorithm to rank pages. Google are specifically measuring time. A slow page speed result means that search engines can crawl fewer pages using their allocated crawl budget, and this negatively affect your indexation. “Site speed reflects how quickly a website responds to web requests.”
Fast Page speed = good user experience. Pages with a longer load time tend to have higher bounce rates and lower average time on page. Longer load times have also been shown to negatively affect conversions and lose customers.
Ways to increase your page speed:
Do not use gzip on image files. Instead, compress these in a program like Photoshop where you can retain control over the quality of the image. See “Optimize images” below.
By optimizing your code (including removing spaces, commas, and other unnecessary characters), you can dramatically increase your page speed. Also remove code comments, formatting, and unused plugins.
Avoid and Reduce redirects
Page redirects to another page, your visitor faces additional time waiting for the HTTP request-response cycle to complete. For example, if your mobile redirect pattern looks like this: “example.com -> www.example.com -> m.example.com -> m.example.com/index,” each of those two additional redirects makes your page load slower.
Leverage browser caching
Improve server response time
Your server response time is affected by the amount of traffic received, resources each page uses, the software your server uses, and the hosting solution you use(shared or dedicated). To improve your server response time, look for performance bottlenecks like slow database queries, slow routing, or a lack of adequate memory. The optimal server response time is under 200ms.
Your images should be no larger than they need to be, that they are in the right file format .png are generally better for graphics with fewer than 16 colors while jpeg are generally better for photographs and that they are compressed for the internet.