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.
As a hero of the mighty Alliance, journey to the seafaring kingdom of Kul Tiras, home of Jaina Proudmoore. Untangle a web of betrayal and dark magic as you encounter power-hungry pirates, witches wielding death magic, mystical sea priests, and more. Explore the stony peaks of Tiragarde Sound, trek across Drustvar’s high plains and red forests, and navigate the intricate inland canals of Stormsong Valley as you convince this fractured kingdom to join your cause.
Download the game right now, create an account (a new one; not your old one, if you were a previous player), and you’ll be able to level your character all the way to 20 for free. There are other annoying limitations placed on this free experience, but it’s still a great way to familiarize yourself with the world, see if you enjoy the experience as much as you were hoping, and get a feel for the different classes before you settle on a main one to play as for the next 100 levels’ worth of gaming.
Picking up herbalism and mining is the best professions to have while leveling. Not only will you earn gold as you level, but you will also get extra XP. At level 20 you will get over 500 XP for picking up a ore or a herb while killing a mob only gives a little over 100 XP. Don’t go out of your way to pick herbs if you are trying to level quickly, but pick the ones that are on your way. Leveling from 110 to 120 can be done pretty quickly just by doing this. There are a few items that will help you if you decide to use professions while leveling:
Most classes in World of Warcraft start at first level, but Death Knights and Demon Hunters are exceptions. They start at level 55 and 98, respectively. This alone can shave a huge chunk of time from your leveling experience. Of course, it only works if you want to play a Death Knight or Demon Hunter, but they’re both solid classics that can dish out damage or tank in a group.
Incursions are a new world content activity that are unlocked when one character has unlocked World Quests. This feature is unlocked account-wide meaning that all characters on that account can access Incursions even without being Level 120. This provides for a lucrative experience acquisition method that is available in a similar pattern to what Legion Invasions offered with nearly an entire level earned by completing an Incursion series which involves four World Quests and one mini-scenario at the end. These also grant item level 370 weapons and Azerite armor, so they should be done any time they are up. Incursions follow a similar schedule to Invasions and are available for 20 hours once they are initiated.
No matter your experience level—whether you’re about to experience the thrill of hearing the Stormwind City theme as you walk through its epic gates for the first time, or whether you can spell Ahn’Qiraj off the top of your head—here are some tips and suggestions for making the most of your new life in the World of Warcraft (or your epic, Illidan-like return to Azeroth.)