If you can Solo an instance, you have two options. The first is to take the place apart yourself and sell all the drops on the Auction House. For level 80 characters, Scarlet Monastery, Uldaman, and other mid-level instances are easily soloable, and are a very popular source of cloth and marketable blue and green items. If you're reasonably well-geared, and feeling more adventurous, Scholomance and Stratholme are also soloable, and can be extremely lucrative as a source of auctionable items.
Potions serve more utilitarian purposes, and it's up to you to decide whether to make use of them. The most common is the Swiftness Potion, which can provide you a handy boost in speed while going after annoying quest objectives indoors. These are generally MASSIVELY overpriced, because people know how useful they are. I opted not to spend the gold since Warriors are already fairly mobile, but slower classes may benefit greatly from these.
The Auction House is always the best option for getting good equipment at a good price. The only items you should be buying from Vendors are basic consumables: food, drinks, arrows, bullets, vials, dyes, etc. Most other things should come from the Auction House, as they are generally cheaper. Keep these tips in mind when buying items off the Auction House:

This top-end difficulty was missing entirely from Legion’s first raid, Emerald Nightmare, which was cleared by top guilds in around 11 hours. Meanwhile the first guild to clear Uldir’s hardest difficulty, Mythic, spent somewhere around 70 hours attempting to kill the raid’s eight bosses. Even after all that time, the guild, Method, still had members say they loved the raid, and that it was one of their favorite in recent memory.
The Auction House (AH) is a brilliant way of making money if you know the tricks on how to do it. The basic strategy with the AH is to buy things cheap, re-list them on the AH, and then sell them for a profit. Even better, of course, is to get good items from drops and then sell them on the Auction House for pure profit. Many players generate most or all of their cashflow simply by speculating on the AH. So a good understanding of the it, as well as some time to invest, is essential to turning it into a money-making proposition for you. It is also highly recommended that you get the Auctioneer addon for quick listing auctions, and knowing the average price of items. Another great addon that can assist you in flipping items for profit on the Auction House is Tycoon. This addon analyzes items on the Auction House such as cloth, ore, and even TCG mounts. Once the information is recorded, Tycoon will inform you of the most profitable items possible, and exactly how much you can make by either farming them, or buying them at their current price and then relisting them.

I dont know if this exist already, if it does I couldnt find one, but it would be nice to have a guide with the location of all daily quest broken down by Alliance, Horde, Faction, Neutral, etc. I know there can be variable quest for things like Fishing and Cooking but just having the location for those quest givers would be great. If it were a stand alone addon that would be even better!
A farm that I myself made drastically popular about 2 years ago.  This farm is a simple pet and transmog spot that requires you to pull the entire wailing carverns instance.  Besides how it sounds, this farm is VERY easy going and can literally be done while you watch something else entirely.  (netflix maybe?)  While it's not as potent as it used to be, it still has some merit in it, especially if your server is low on the deviate hatchling pet.  While it does take some time to drop, I can usually average  a deviate hatchling every 30 minutes or so.  However, since I released the video on it, the price of the pet has dropped wildly.
Similar problems have risen in the leveling system, which automatically scales to the player’s level and equipment. For the most part, you’ll vaporize enemies more quickly as you gain power, but there are some weird dips. Many players complained they felt less powerful at level 119 than at level 110, a problem I experienced myself. And world PvP remains a strange and whacky world where level and class balance issues make wins and losses feel destined instead of earned.
Formerly, when you visited a new zone, you would be very careful, tiptoeing around, cause everything was higher level than you. But as you dinged (leveled up), you would get more powerful relative to the locals. So you would feel more confident and capable. Dinging came to represent more HP, more Mana, better hit ratio, more crits, more talent points. you felt REALLY good when you dinged, like you had accomplished something. Almost tangible. You would think "now I can go back and take that mob/group that ganked me". And then when you had done all the quests, you would move to another zone and do it again. Fun!
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