Keep in mind I’m speaking from the horde side of things, things may be different for the Alliance but for horde it goes kinda like this :-
For classic it kinda depends on your race. For example the forsaken start in Deathknell, move to Tirisfal Glades then to Silverpine forest that leads to Hillsbrad foothills and then continue the effort in Arathi Basin That then lead to the hinterlands, after that you free roam doing missions for your factions until you are level 50, then you start in Western plague lands and move to Eastern plague lands for the forsaken finale.
For TBC you all start in Hellfire, move to zangarmash then move to terrokar forest then Nagrand then blades edge mountains, then shadowmoon valley and end in netherstorm, I think the blades edge mountains and shadowmoon valley could be in reverse order or interchangeable, don’t remember correctly.
For Wotlk, you actually have the option to start in one of two places, Either borean tundra or Howling fjord, which then lead to dragonblight and grizzly hills, which then lead to Zuldrak, a mini quest to discover dalaran in crystal song then you head to sholazar basin and then into icecrown for the finale, you can visit storm peaks but back then you only could complete a handful of quests before max level there.
For cata you either started in deepholm or Vashjir, then moved to Hyjal, then to Uldum and then the finale was in Twilight Highlands.
For MoP you started in the jade forest, then moved to the valley of the four winds, karasang was kinda optional, from then on you go to Kun-lai summit, move to Townlong steppes and the finale is in the dread wastes.
For WoD you started in tanaan jungle then moved to your respective faction start, frostfire ridge being the horde’s and Shadowmoon valley being the Alliance’s start, then they move to gorgrond Followed by Talador then into spires of Arak and the finale happens in Nagrand.
For legion the starting point is Optional and the actual lore of how things happened is vague, some people hinted at it being broken shore > Class questline > Aszuna > Stormheim > Highmountain ~ Val’shara > Suramar.
For BFA it’s the same as legion, the order is vague and you can start anywhere, but it’s know you don’t actually quest in the other faction’s islands unless its for the establishing a base which happens at the respective level they’re available at.
Hope I helped!