If you want to spend as little time on your alt as possible - just do Legion Invasions. You can use sites like (https://wow.gameinfo.io/invasions) to track when the next invasion will be. Log in, fly to the closest world quest, and once there - right-click on the quest's name in your quest log and "Find Group". Sign up for some group, or if there's none - just start your own immediately, and people will come to you. It is 10 times faster to do invasion quests in a group. Once that particular quest is complete - leave the group, and fly to the next one, where you should find another group. Don't expect the group from one world quest to follow you to the next. Then you simply log out until next invasion. You can do 1-2 invasions a day, and each invasion will give you about a level or 1.5 of experience, if you have full heirloom gear. Each invasion will take about 20 minutes.

NOTE: It is VERY important to not vendor any equipment you pick up. You will be deconstructing all of your gear for resources that will help you in the Warfronts to be fought! Deconstructing, or scrapping, your gear will be done using the Scrap-o-Matic 1000 if you are Alliance and the Shred-Master Mk1 if you are Horde. This works the same as the way the Obliterum Forge worked in Legion. The scrapping feature can be used on all Battle for Azeroth equipment found, not just craftable equipment, so save everything you acquire for the scrapper! Before we get started, keep in mind some of the tips below that can speed up your leveling process!
There are times when you will be fighting things a couple of levels higher than your character. This is easy enough for some, but others might find that they need to be a bit more careful. If you let yourself get a couple of levels ahead of the guide then this ceases to be an issue. If you look through the configuration options you’ll see a place to set your difficulty rating. 

"Since [patch] 7.3.5 we’re happy with the overall pace of leveling, he said. "If you’ve chosen to start a brand new character right at the end of an expansion, getting a character fully leveled up and geared up to complete endgame content before the expansion ends, there’s always going to be some time pressure there. That’s just part of the nature of choosing to do that at that stage in time."
Hopefully, you have a good idea how you want to begin your endgame experience in Battle for Azeroth. A whole new set of content will drop on September 4 when the Uldir raid opens up and the PvP season begins. That also marks the beginning of Mythic+ dungeons in BfA. Even after that happens, many of these tips and strategies for gearing up will still be the best sources of early gear for your new 120 characters.
Patch 8.1 has introduced new reputation items that can be purchased using Seafarer's Dubloons earned in Island Expeditions. These items can be purchased for 100 of the Seafarer's Dubloons and grant 250 of the reputation linked to the item purchased. This can be used as a great catchup mechanic for reputations needed for the primary reputations in Battle for Azeroth. The specific items can be found in each of our reputation guide pages.

I wouldn't buy Zygor guides. As a player since path 1.10 (around 7 years now) Ive seen a hearty wow community flourish through each expansion. I am a huge fan of the add on, Carbonite quest. It provides a pumped up version of wow's internal quest database. Also, its recommended to research your servers economy for making gold. http://www.powerwordgold.net/ is a great site for tricks of making gold. Pair it up with http://www.theunderminejournal.com and you'll be on your way to making fast gold to provide for all them alts :P 

-New dungeons- About 3/4 are fairly decent, not too long not too short, but none of them are compelling, none make me say to my friends and guildies, "Hey, let's do this instance, I love the theme and encounters." They're dull but tolerable. The other 1/4 of the dungeons just aren't fun and you will groan when you get a mythic Keystone for the Underrot, the snake temple, or Waycrest Manor. Waycrest Manor is actually one of the better dungeons, however, with the new Infested affix, Waycrest Manor suffers from many game-breaking bugs that end in the entire instance being pulled due to doors not properly working as intended.
Plus, I am a pet collector, and there are plenty of pets to collect in the new dungeon. Completing the dungeon’s challenge mode grants players a Mini Spider Tank battle pet. Continue playing on a weekly basis to earn currency towards items like the Unopened Gnomeregan Supply Box, Mechanical Cockroach, Schematic: Mechantula, Leper Rat Tail, and Rechargeable Alarm-O-Dog Battery.
Incorporating an accelerated leveling pace is *definitely* something we want to incorporate in to the new addon  My hope is to allow an option for you to set yourself to one or two higher speeds, where the guide will skip some steps along the way. The steps will have a special tag that lets the addon know to skip them if the person has that setting enabled.

Valid pieces for Azerite empowerment are available for the chest, shoulder, and head slots of all classes. This equipment has multiple tiers of that can be unlocked, represented by a series of concentric wheels with icons representing individual powers; as individual powers are selected, they rotate into slots at the top of the interface, activating the selected benefit and locking out the others unless the player pays to reset their decision. Outer rings offer multiple choices, some based around the character's class and specification, others around the zone or circumstances in which the gear was acquired. The innermost circle offers no such options, instead being a boost to the level of the item itself, and thus providing a flat all-around benefit.
[Expulsom] is obtained primarily from scrapping armors and weapons using the Scrap-o-Matic 1000 (Alliance), or the Shred-Master Mk1 (Horde). These tools work like disenchanting, you can break down any gear obtained that is from the Battle for Azeroth expansion, including dungeon/raid drops, quest rewards, world drops and crafted gear. The Scrapper isn't restricted to specific trade skills. Anyone, even people without a crafting skill can use it. You will mostly get ores, gems, leathers, cloths, and occasionaly you will get one [Expulsom].

If you queue as a healer - take care to always have a stack of water of appropriate level. You can buy it at an innkeeper for next to nothing, but remember that it will become too low-lvl for you very fast, so you need to buy new water every 10-20 levels. Alternatively, you can buy a stack of every tier of water in Stormwind, and just always carry it with you. Another alternative, if you see a mage - always ask him (politely) to create a table for you. Grab 2-3 stacks so you have extra for the next runs.  

A: We chose to go with the subscription-based model instead of that approach. We've taken the approach that we want players to feel like it's a level playing field once they're in WoW. Outside resources don't play into it -- no gold buying, etc. We take a hard line stance against it. What you get out of microtransactions is kind of the same thing and I think our player base would feel betrayed by it. I think that's something else you have to decide on up-front instead of implementing later.
I also noticed that the slowdowns were heating up my graphics card (a GTX1080 with good cooling and a well-configured fan curve). On high but not max settings, I would always hover around 60-65 degrees C, and thought this was normal. After turning auto zoom off, I noticed that my card never gets past 49 degrees C. I'm pretty shocked, as it's a very hot day where I am and I didn't know one feature could affect temps so much. I didn't know my temps could even get that low! Even on full max settings (with 200% resolution scaling etc.), it now can't go over 66 degrees, whereas it used to go up to 74 degrees at times when auto zoom was on.
At the end of Legion, the titan Sargeras was imprisoned, but not before he plunged his sword into the planet Azeroth. This not only devastated a massive area (much of the desert zone of Silithus is now cracked and scorched), but badly wounded the gestating titan inside. While the heroes managed to ablate the worst of the damage (at the cost of the majority of their artifact weapons' mythic power), the world is still wounded and bleeding a substance called "Azerite," which has great magical potential. The Horde Warchief, Sylvanas Windrunner, attempts to consolidate Horde power on Kalimdor and gain a monopoly on Azerite (which is primarily found at the southern end of the continent). Her campaign to do so, the War of Thorns, formed a pre-launch event for the expansion and ends with the major Night Elf holdings on the continent seized or (in the case of their capital city of Darnassus) annihilated. The Alliance makes a retaliatory strike against her home base, the Undercity, which was formerly the human capital of Lordaeron. This succeeds in driving the Horde out, but before leaving Sylvanas saturates the area with disease and toxins that render it uninhabitable. With this tit-for-tat military exchange, the Horde has almost complete control over Kalimdor, while the Alliance has near-total dominion over the Eastern Kingdoms.[4] With further conflict inevitable, Battle for Azeroth takes the two factions to the continents of Kul Tiras and Zandalar to recruit new allies in order to turn the tides of war.[4]
There are times when you will be fighting things a couple of levels higher than your character. This is easy enough for some, but others might find that they need to be a bit more careful. If you let yourself get a couple of levels ahead of the guide then this ceases to be an issue. If you look through the configuration options you’ll see a place to set your difficulty rating.
Engineering has the option at skill level 200 to specialize in Gnomish or Goblin Engineering. You can get the quests from your Engineering trainer. The main difference between both sides is the location of their respective teleporters and the ability of their trinkets. Some items require a specific specialization to use, while other items are crafted by one specialization but are usable by any engineer. Fortunately, most recipes that are crafted by one Specialization can be worn by both.
The leveling experience for the Burning Crusade and Wrath of the Lich King levels of 60 to 80 has been greatly reduced from 6,689,030 XP to 4,412,600 XP which is a reduction of 34%. This has been a notoriously lengthy leveling section, and this reduction will be very noticeable and appreciated by those players leveling new characters such as those allied races!
Professions skills are split between expansions now, you'll have a separate skill bar for each expansion. There are still 950 profession levels in total, just that there is no one single progress bar with 1 to 950 for it anymore. Instead, there are 8 separate progress bars. (The only exception is Archaeology, because it will still have a 1-950 progress bar)
How is this better than the in-game quest helper thingie? While that shows you the destination of your quests it doesn’t show you the best order in which to take them, which to skip, and when to move on (such as when you’ve out leveled the area.) .  Zygor’s show you the optimum path to take to complete the most quests in the least time, which will save you lots of time over the quest helper.