As always, I will monitor and update this guide as new information comes in. If I've gotten anything glaringly and completely wrong, just tell me with as much data as possible. The idea is to find the fastest possible leveling method, NOT to argue about how good or bad individuals are. If you have hard data, post it! If you have an idea, let the thread know so we can test it!
There is an alternative really cheap method, but only Blood Elves can benefit from it. Due to their Racial Ability it allows them to gain ten free skill ups by converting a Large Prismatic Shard into three Small Prismatic Shards and back again. Only the conversion from one Large Prismatic Shard to three Small Prismatic Shards is effected by this. Therefore, you will only have the chance to gain skill ups half of the time (since the other half of the time you'll be converting back to three Small Prismatic Shards). This can make for a fairly lengthy session in gaining your ten free levels.
As an example, I will take my server values to calculate how many procs you need to make up the price of one Magnetic Mining Pick (40 SS ore, 10 Platinum ore, 15 Expulsoms). Assuming 25g per SS ore, 20g Platinum Ore, and 55x the price of Tidespray linen to craft 1 expulsom in average (got the value from a previous post in this subreddit); 1 Pick is worth 5325g (not counting the elemental flux).
Island expeditions - Set sail for the previously unmapped isles of Azeroth. Battle in groups of three as you race against cunning rival intruders—or enemy players—to collect the island's resources. Constantly evolving challenges await as you traverse frozen landscapes near Northrend, open the gates of an abandoned Gilnean castle, navigate a war between elementals and more. Can be done either in PvP or PvE against advanced AIs.
3. When messaging these players, it is important to remember that they too are people and are looking for emotional connections in their social lives. Having a name without mart or sell is only the first step. Do not approach them and immediately spam them with "need gold plz"! Say hello, ask them how their day is going, etc. After you establish this basic interaction, most will ask you how you are doing. The most successful phrase I have seen has been "I am doing well thanks! I am new to this game but I like the people here very much. I saw I needed to buy skills but I'm not quite sure how to make money. Would you mind helping me please?".
The Alliance are able to unlock the void elves (exiled blood elves who can tap into shadow magic, trained by Alleria Windrunner after her experiences on Argus), Lightforged draenei (draenei members of the Army of the Light who fought the Legion on Argus), Dark Iron dwarves (fire-blooded cousins of the in-game dwarves of Ironforge), and Kul Tiran humans (larger, more heavyset versions of the in-game humans of Stormwind).
This farm almost did not make the list, since every YouTuber and farmer alike has beaten it to death since it first appeared sometime in 2012. There are so many videos on this spot, that it's hard to to stumble across one, even while searching for something completely mundane, like chicken wings or golf clubs. Anyway, you want to pull the entire instance without aggroing any of the bosses, and if your a skinner you an make slightly more gold by skinning the hides. Generally this farm is being phased out by the lvl 58 twilight outpost farm, and with good reason. It's better and does not require you to enter the instance. So more drops for you! Not sure, why anyone would pick this spot over the latter unless you were really interested in increasing you skinning level.
Once you have your potions, proceed to complete all the bonus objectives in your starting zone. This should easily level you to 92, where you can proceed to Gorgrond. Interesting enough, for some reason many Gorgrond quests are worth nearly double the experience of quests in other zones. Maybe this is a bug, maybe intended, I'm not sure. But I actually recommend you do all the quests and bonus objectives in Gorgrond. For your outpost choice, I recommend choosing the Gladiators, since they give access to more treasures than the shredder IMO.
I recommend not counting on transmog sells for your monthly gametime. Its a great market, but also pretty random. You have to have the right items posted at the right moment if a player needs a certain item. If this is not the case, of course you will not sell anything to him. There are people making millions of golds a month with transmog. But they are very professional at it and it really takes a lot of time.