This is also the reason why when I read in WoW forums of people skipping guide sections, due to being too low level I'm not agree and start ranting about it: it'll be a mess syncronizing with the guide and I've seen many people complaining about missing quests or accusing the guide for being innacurate, but not realizing that was their fault since they're skipping and missing a lot of quest chain requirement. Of course this apply if you're following a guide, believe me, it's very frustrating when you remain stuck in a guide section due to the reasons I've mentioned, more than doing grey quests (but they allow to be perfectly in sync with the guide) and goiing here and there to get the pre-requisite quests.

Fifth: As for Azerite Armor, I recommend getting the Chest first from Magini and if you do Vol'dun first, the first piece you can get will be a Head and the final piece from the zone with be Shoulders. That will give you all 3 pieces of Azerite Armor when you leave the first zone which will help out. If you are leveling a different spec from what you plan on playing, (i.e leveling as a dps when you plan to heal/tank) you will receive at least 2 pieces from every zone then 1 piece from starting the War Campaign that you can choose your Main Spec trait for. Pick the traits that will help you level the fastest.
"The way the glyph market works on most realms is that there are a couple of people willing to put in the long hours who will have every available glyph posted profitably, and undercut within minutes of being undercut. They all reduce the price very minimally when undercutting, and the "competition" isn't about price, it's about who can relist more frequently.
If you have a lot of gold, you can use it to pay other players to do some of the game’s less exciting activities, like fishing, herbing and mining. Some high-end guilds like to amass large stashes of gold so that they can provide consumable crafted items like stat-enhancing alchemy flasks and cooked food items that buff players, as well as enchantments and gems, to their raiders.

Professions: This may seem strange for a leveling guide, but the first opportunity you get, pick up both the Mining and Herbalism gathering professions. Not only will this allow you to track many various quest objectives on your map, but you also get a fair amount of experience whenever you gather. I'd put it at around 10% of a quest turn-in per gather. Since most of your wasted time in WoW is travel time, stopping to gather ore or herbs can keep your exp/h rolling as long as you don't go too far out of your way. You should only gather if it's convenient, and on the way to an actual quest objective. Don't make gathering your priority.

Something to keep in mind as well is that this will make enchanting materials more valuable, since it is likely most players will now simply scrap their boe greens instead of getting them disenchanted. Also redundant dungeon/raid gear can be scrapped rather than traded to the (guild) enchanter in the run. Less stuff gets disenchanted, meaning there will be less ecnhanting materials, meaning their value will rise. All the more reason to DE rather than scrap as an ecnhanter.