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.
Many players who already have higher level characters create alts that they level to a certain point and then stop. Often, these twinks are level 18-19, 28-29, 38-39, etc. for the purpose of going to battlegrounds at the top of their tiers and kicking butt. Since these twinked characters are owned by higher level players with lots of cash, they usually outfit them with the best gear available at their level. Thus, items that require level 17-19, level 27-29, or any other items around this level, with good stats or dps, often sell for much higher prices than they normally would. This is especially true on an older server, and also especially true of blue (rare) items. In general, "good stats" include Cloth "of the Eagle" (for mages, warlocks), Leather "of the Monkey" (for hunters and rogues), and Mail "of the Bear" (for warriors/paladins)as well as weapons with these suffixes that can be used by the right class.
Flipping is the least time consuming way to make gold in WoW. It simply involves trading on the auction house. You buy low and sell high. There are a lot of different markets you can try your hand in flipping both Legion and old world. Flipping works best when there are natural variations in either demand or supply for an item which will cause the price to vary over time.
This is a VERY GOOD potion of treasure finding farm that generally shocked me when I stumbled upon it. In this video it's one of the more popular farms – just because it's potential to tap into soo many different markets (especially if you are a skinner). It takes place at the pit of scales near the foot of the uldum river. It allows you to not only gather tiny treasure chests faster than any other spot, but also awards an obscene amount of leather. Just step on the eggs and 5 crocolisk will attach to your character. Kill them all and start skinning them. There are 6 egg spawns with very short respawn timers surrounding the area. You will literally never be waiting for respawns. Again, skinning is a must to take advantage of this mega spot – and even though, I feel only a handful of farms surpass this one, It's truely my favorite.
The best way to collect AP is through world quests, a system that allows players to complete menial tasks to earn moderate rewards. A finite amount of AP spawns on the map through these quests — generally at least 2,000 a day. I’ve likely done most of these quests close to 20 times in the course of preparing my various characters in the 45 days since the expansion launched. In some cases, I’ve replayed them as many as 50 times.
It's hard to step out of the shadow of Legion, which was utterly fantastic in almost every way, to enter an expansion where you get one item per boss in the last expansion because the rules have been changed to force more grinding, where you have to grind reputation in the old expansion that you probably skipped because rep grinds suck JUST to unlock allied races (who aren't fully unique races since they recycle old content such as animations), where questing has SOMEHOW become boring again and where your new abilities are given by items you'll swap out every level, meanwhile being only boring passive effects no one cares about.