I've never been happy with the PI documentation, book or Harry's vids for learning PI. You can pick up great bits from the forum, if you can recognise them. I'd suggest the
light vortex tutorials which are well written with good screenshots so you can see what each substep is doing. At the bottom of that page are two Example tutorials which are really complete workflows from starting data to final image. I highly suggest you work through those with your own data so you understand what each step does and what settings are good for your data in particular. As with anything in PI adjustment basically depend on your data, so "use this starting value" suggestions dont work universally. but once you find them for your data you can reuse them or use them as starting points for future captures with the same gear.
The other light vortex tutorials work through from the top down and they work like that as a complete workflow too. Don't ignore any as the substeps themselves are valuable to understand even if the dont immediately apply to your current image. Take notes, for example reducing noise, boosting contrast, boosting faint signals can all be done in multiple ways in PI, and are often intermidiate steps in the LV tutorials rather than specic noise reduction, boost contrast, etc steps. The tutorials are long and detailed with good explanations, even pros and cons to differing methods for the same purpose. I've been reworking my PI workflow with pieces from LV to end up with improved images (using older data I already processed) and its made a huge difference and well worth the time and effort.