Congratulations on reaching Level 120! Now that you have hit Level 120 we recommend looking at our Easy mode page and Talents section to learn how to play at max level. To get yourself prepared for the end-game content ahead, we strongly recommend this Battle for Azeroth Raiding Lexicon/Spreadsheet by Medivh. It is a gold trove of information that will help you when gearing up in Battle for Azeroth and more.
Edit 20 It’s been a week since this post and a lot of people are still reaching out to me with questions which is fine. I have had a few different people reach out to me to help make YouTube videos based off this guide and more info in BFA which I’m more than willing to do. Whoever gets the videos up first I will link them here for you guys to enjoy.