Every resource a Sunwaver needs to build real plumbing skills, the reading and the booklets, in one place. These are supplemental, though: much of what you learn will come on the job, working alongside your trainer.
Work through each level in order. Plan on about two months at each level, so you have time to cover everything, review it, and get tested before you level up.
Four levels, so roughly eight months from Level 1 to Level 4. Each level gives you the time to cover everything well.
Go through every booklet and every chapter: read it, discuss it with your trainer, take the quiz to check what stuck, and then have your trainer test you.
Have all of the level's material covered, reviewed, and tested, then test up to the next level.
You'll notice some material comes up more than once across the booklets, chapters, and levels. That's on purpose, the things that repeat are usually the things that matter most, so seeing them again helps them stick.