Enable caching is one of the most simple and useful techniques to increase site speed. Caching allows for webpage elements to be stored on your hard drive’s cache memory or temporary storage. This enables the browser to load the page from cache memory rather than making another request to the server the next time user visits the site page. As such, caching decreases the request size of the webpage. Content that is cached is loaded from the cache memory instead of the server.
There are some plugins also available that caches whole html of the page on server storage and then serve that html every time the page is requested. While using caching, make sure to clear the cache every time you change any contents of the site to reflect them on the website.
We started using the WP Super Cache plugin. Based on the recommendation of a new hosting partner we switched to W3 Total Cache plugin. That was still eating into our Pagespeed so we eventually ended up using the Autoptimise plugin.