Rule Books

For this campaign you can use the following:
Player's Handbook (roll20 + print + pdf) Xanathar's Guide to Everything (roll20 + print + pdf) Tasha's Cauldron of Everything (roll20 + pdf) Valda's Spire of Secrets (print + pdf) Level Up: Adventurer's Guide (pdf)
The parentheses are what I have the content on and can share with you. 
What is Valda's Spire of Secrets?
This is a 3rd party rule book that does a great job of adding a bunch of new character classes, subclasses, spells and a bunch of other content.
What is Level Up: Adventurer's Guide?
This is also a 3rd party rule book, but it tries to add on to not just character classes, but d&d 5e rules all together. In the 80s there was dungeons and dragons and advanced dungeons and dragons, this is commonly referred to as Advanced 5th Edition or A5E for short. All the new rules really do is add more options, for the most part you can ignore it if you want.