Bookwise, the recommended route is Learn Windows PowerShell in a Month of Lunches, followed by Learn PowerShell Scripting in a Month of Lunches..
If you search powershell.org for scripting games you’ll find a bunch of archived puzzles to test your skills.
PSKoans is a resource which takes a different approach and teaches you PowerShell via Pester unit testing.
For more challenges see here: https://ironscripter.us/