I’m not sure it’s entirely possible to do everything in order. (I know that the BfA intro can mess with the Cataclysm intro quests.) But, you can get pretty close.
First, you’ll need to decide if you want to keep things challenging or one shot stuff as you quest. (Given the sheer number of quests in the game, I’d recommend the one shot option just to keep your sanity — it also makes it easier to just solo any quests involving dungeons and raids.)
It will be easier if you have access to Chromie Time, but it’s not necessary. Chromie Time lets you turn on scaling for all of the old expansion content up to level 50. Chromie is near the Embassy in Orgirmmar and Stormwind. There’s an hourglass icon on the world map at her location if you have access to Chromie Time. You need to have a character already at 50 before your other characters will have access to it.
When you turn it on, you pick an expansion (the old 1-60 zones are part of the Cataclysm expansion.) Which expansion you pick sets which dungeons you see in the LFD tool. No matter which expansion you pick, all of them will scale to 50, so it really only matters for the dungeon tool. You can swap your expansions at any time by talking to her again. You can also turn it off and back on. Once a character is 50, they lose access to Chromie Time. (Also, once you get access to the Shadowlands starter quest at 48, it also becomes a bit more annoying to use.)
You can turn off your XP gains at any time for a small gold fee. (The same NPC can turn it back on.) You just need to talk to Slahz (Orgrimmar) or Behsten (Stormwind). Regardless of if you use Chromie Time or not, I’d turn off XP at 47. This will prevent the Shadowlands intro from messing with stuff, it will also minimize the interference of level 50 BfA content phasing in some of the older zones. I’d turn it back on after you’ve done the Legion intro.
Finally, without Chromie Time, the old expansions scale in the following level ranges:
Low level Kalimdor and Eastern Kingdoms: 1-30
Burning Crusade and Wrath of the Lich King: 10-30
Cataclysm (Hyjal, Vashj’ir, Deepholm, Uldum, Twilight Highlands): 30-35
Mists of Pandaria: 10-35
Warlords of Draenor: 10-40
Legion: 10-45
Battle for Azeroth: 10-50
Once you get 5 levels above the cap (with the exception of BfA) you’ll start getting an overlevel bonus that will give you extra damage and damage reduction from mobs. (You’ll also stop getting meaningful XP by that point.)
Note: If you really want to start at the beginning, load up the Classic client. The old 1-60 content got revamped in Cataclysm, so the only way to do the Vanilla content now is through Classic.
If you are starting with something other than a Worgen/Goblin/Pandaran, Death Knights, Demon Hunters, or Allied Races I’d start with Exile’s Reach as your starting zone. I’d then continue the tutorial and do the BfA intro up through getting the “Welcome to Zandalar” or “Come Sail Away” achievement. The reason I recommend it is that it will minimize some phasing weirdness for other stuff. When you get around to the BfA expansion in your tour, you can always make a dummy character to go through the intro again as a refresher of the story.
With Worgen/Goblin/Pandaran if you want to to their starting zones, you can’t do exiles reach. While starting with their zones will take you out of order timeline-wise, they all have good story worth doing.For Allied races, Death Knights, and Demon Hunters, Exile’s reach isn’t an option as they start at level 8-10. I’d still recommend doing the BfA intro any of these character once you get to the main city. (You can pick up the quest from the Herald next to the Warchief’s Command/Hero’s Call board.)
So, since everything but the old 80-85 cata zones can be done at 10, it’s pretty easy to do stuff in order beyond the starting zone stuff.
So, a quick overview of the order:
Blood Elf/Draenai starting zones
Outland (Burning Crusade)
Non-allied race DK starting zone
Icecrown (Wrath of the Lich King)
Goblin and Worgen starting zones
Low level Kalimdor and Eastern Kingdoms* (Cataclysm)
Hyjal, Vashj’ir, Deepholm, Uldum, Twilight Highlands (Cataclysm)
Pandaran starting zone
Pandaria (Mists of Pandaria)
Draenor (Warlords of Draenor)
Demon Hunter starting zone
Broken Isles (Legion)
- The old 1-60 zones got revamped in Cataclysm, but how revamped varies greatly. Some zones like Silverpine Forest and Burning Steppes got complete quest redos. Some got some story updates but still have a lot of the old questing “bones” intact. And some just got a bit of clean up but no real updates. The updates that did get made are very Cata timeline specific which can be really weird at times since the main cities moved forward to the Shadowlands timline.