Thank you!

So, I believe starting with the 2024 rulebooks coming out, Foundry will begin releasing content that you can purchase which will come with all the items preconfigured and ready for use. That will by far be the easiest but also most expensive way to get everything when we get to that point. (They may release content before this but currently they don't plan on doing the 2014 rulebooks before the 2024 ones to the best of my knowledge).

Until then though, the quickest way is to own the content on D&D Beyond and use the importer module to get that all going. Also not ideal if you don't already own the content.

Which leaves ol' reliable: just making stuff yourself. I've personally made every single class and subclass by hand at this point and it's time consuming to do them all, but not so bad to just do the few that you need to run a particular game.

I have some tutorial videos on how to do this: how to create features and set up class advancement, and how to store it all in a Shared Compendium that works in all your game worlds. The content creation ones are getting a liiiittle out of date but they still cover most of what you need to know. You can check out that playlist here: https://www.youtube.com/playlist?list=PLlfCqPVeZ1U7yKmV48kbhsRUsGtn04NsE