In particular, between 2014 and 2016, it was possible for dedicated players to generate quantities of gold that were previously impossible to obtain, and have not been possible to obtain since. The Warlords of Draenor expansion was the first time the game included nonplayer character followers that players could send on missions to collect resources, items and other useful stuff, including gold.
Pick druid, paladin or monk. Get heirlooms if you can. Grind mobs until level 5 - 6. Start doing the easy "just kill these mobs outside town" quests until 15. Queue rdf as every role and do every dungeon you can (with heirlooms you could probably solo the dungeons) while you travel to higher lever zones. Keep doing the simplest quests while you're waiting for rdf (which shouldn't be long). I leveled a druid to 100 once doing this in maybe a day /played, but he was also rested for most of the process.
Earthen Ring - Alliance Earthen Ring - Horde Echsenkessel - Alliance Echsenkessel - Horde Eitrigg - Alliance Eitrigg - Horde Eldre'Thalas - Alliance Eldre'Thalas - Horde Elune - Alliance Elune - Horde Emerald Dream - Alliance Emerald Dream - Horde Emeriss - Alliance Emeriss - Horde Eonar - Alliance Eonar - Horde Eredar - Alliance Eredar - Horde Executus - Alliance Executus - Horde Exodar - Alliance Exodar - Horde Eversong - Alliance Eversong - Horde
As always, I will monitor and update this guide as new information comes in. If I've gotten anything glaringly and completely wrong, just tell me with as much data as possible. The idea is to find the fastest possible leveling method, NOT to argue about how good or bad individuals are. If you have hard data, post it! If you have an idea, let the thread know so we can test it!
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.