Is there a template that shows how one can manage a WPO project? Like what to look for first and the types of tests to run.
The things to look for vary by site - there are general principals (minimise requests, enable HTTP compression etc), but the actual tasks required to speed up a given site will depend on how the site was constructed - which CMS it was built on, what extensions or plugins are installed and how the theme itself was created.
Learning to read the waterfall charts is a good idea - although you could get by using Google’s Webpage Speed Insights:
https://developers.google.com/speed/pagespeed/insights