Though related, this is no longer true. You can now purchase a lvl 90 character boost. Some power levelers have hoped for a day when you could use real money to buy individual items in-game, some times called "micro-transactions." At a Game Developers Conference 2008, Rob Pardo gave a strong indication, Blizzard would not ever go this route with World of Warcraft.
At 98 you have the option to drop what you're doing and return to your capitol city to start the quest for your Legion Artifact weapon. However, I do not believe this is necessary to do right away unless you're struggling with kill speed in your current gear. I would recommend waiting for a natural pause, such as hearthing to repair and clear your bags. From 100 to 107 you won't even really fight mobs that often; only just enough to clear the way to any treasure you need to pick up.
The zone you start in isn't under your control, in as much as it's pre-selected for you based on your race. But for leveling purposes we want to make scaling work for us as much as possible. That means sticking to the lower level zones. Even though scaling will increase the level of the quests and mobs in those zones, the layout and design of them is built for a player with no mount. So you'll blaze through them and gain more exp/hour than higher level zones which assume you DO have a mount.
Fourth, beginning in Mists of Pandaria with the Halfhill farm, and continuing in Warlords of Draenor with various garrison buildings that produced resources, Blizzard has been making trade goods more plentiful and easier to obtain. In Legion, herbs, fish and enchanting materials were so abundant that a very small population of gatherers could supply more raw materials than the economy could consume.
I'm with that guy, I'll probably pick whichever zone I want and not follow a set path for the questing experience itself (like the part about not picking up the treasures, if I see a shiny I'm going for it lol), but I'll come back to this post for the gearing/rep-gain stuff. Thanks for taking the time to type it out. Also the bit about scrapping gear instead of selling it was something I hadn't thought of so thanks.
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