It’s a good thing that the previous expansion, Legion, was the best in the game’s history because Battle for Azeroth is coasting on its success. The major class redesigns that happened then remain in effect (though some are a little worse, and some a little better), and the combination of World Quests and Mythic+ dungeons means there’s always something to do, no matter your skill level or how long you can play.
One thing to realize is that once you hit 15 you have a lot more options for speedy leveling. Right now (you seem to be level 9 at the time of this writing) you only have questing and grinding, which are inefficient. Once you get the ability to use the Random Dungeon Finder (often called LFD, Looking for Dungeon) you can queue for dungeons in between questing. Often one dungeon, up until 25 or so, will give you most of a whole level off the XP and quests within.
A little bit about myself for credibility: I am a 21 year old college student and have been playing WoW since it was first released. I have three characters at the gold cap and want to share my methods with you in a way that I hope has been more clear and concise than the other guides out there. Thanks again and check back soon for my role-playing guide for WoW as well as other guides for MMOs and RPGs in general.
This farm almost did not make this list. Even though I have had only a little luck with it, it seems to be gathering some popularity in the gold farming community. Although I feel with the recent changes in 7.3, this farm is very close to dying out. Generally what you want to to do is pull every mob you can as you venture to the last boss in the instance. The only saving grace of this farm (if you can call it that) is that some mobs are GUARANTEED to drop greens. Guaranteed. Whether or not they drop profitable greens is a different question, however it's a must-mention quirk you get from running this instance. It also allows you to get your hands on some rare low level blues.