Level with a pet if you can because it will help keep you safe. If your pet is tanking all of the damage from the enemies you’re fighting, you won’t have to. The other reason is that pets are easier and cheaper to heal than you are. If you don’t have a pet, make sure you know how to use your defensive abilities. You can’t level quickly if you are dying all the time.

Même logique que du côté de la Horde, Drustvar est la zone la plus difficile, et la Vallée Chantorage la plus facile lorsque les choses se corsent. Nous vous recommandons également d'attendre le niveau 120 avant de lancer la Campagne de Guerre, puisque celle-ci va juste vous faire sortir du sentier. Nous vous conseillons également de ne pas tuer de monstres rares ou de récupérer de trésors, puisqu'ils ne sont pas si rentables que ça. L'équipement trouvé sur les monstres rare est en plus meilleur à plus haut niveau grâce au scaling : une raison de plus pour attendre d'être niveau 120 avant de les tuer !
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.

There are several reasons why this may have happened. First, only a fraction of the players who interact with the auction house buy or sell WoW Tokens. While the value of both gold and commodities plunged relative to real money, the value of gold and commodities remained steady relative to each other. Players who didn’t interact with the Token market could buy the same number of flasks by doing the same amount of world quests, or selling the same number of gems or enchantments, so these sellers saw no reason to raise their prices.

So this is all from my understanding but with the scrapper it seems to be that you get materials based on the type of gear that you are scrapping. I.E I got more ore from scrapping plate gear and more cloth from scrapping cloth gear. Trinkets, weapons, and rings give different types of material and I don’t quite know the layout for that. Personally I would just DE everything as an enchanter. I stressed how important it is to trade with other players to get the materials needed to do all 11 warfront quest and you will obviously have more materials to create the enchantment that is necessary for the turn in to make trades with.
In 2015, Blizzard started letting players buy gold from each other using WoW Tokens, to try to control the process and mitigate damage. “Time is money, friend — but sometimes one is harder to come by than the other,” Blizzard says on the official page. “Now World of Warcraft players can use the WoW Token in exchange for game time or Battle.net Balance!”