I've been using this since cata, but it has changed a bit since Mop. Maybe it's a re-post but i'll go in depth a lot more.
Professions Used
Mining(Optional)
JC
Alchemy
Enchanting
600 Maxed on each to make things easy.
I say Mining is Optional because you can either farm your own ore (or bot

), if you will not do either than you can always buy it from the ah.
I usually Start with ~60 stacks of Ghost Iron ore( Maximum BO price: 50g/stack) 50*60= 3,000g
Then with all of these ore, you will want to prospect them all. I recommend using Keyspam, so you can enter what key to spam and just afk while it prospects.
After all of the ore has been prospected, change all of the Sparkling Shards, into Serpent's Eye as you may need them depending on your servers price.
Usually, I do not get many Vermilion Onyx while I mass prospect, maybe around a stack for all of those ore so I send those to My alchemist.
How ever many Vermilion Onyx I have, I send the same amount of Wild Jade, and Imperial Amethyst to my Alch to transmute them into Primal Diamonds, i also recommend Transmute Master for this because, I had mats to transmute 10 primal diamonds once, and ended up with 18. Good Procs.
The Meta Gems I usually make that sell the most and fastest on my server (Can Change depending on yours):
Agile Primal Diamond
Austere Primal Diamond
Burning Primal Diamond
Reverberating Primal Diamond
Revitalizing Primal Diamond
If on a pvp server you can throw in a
Powerful Primal Diamond Since Healer's Typically Use that.
Cut Primal Diamonds on my server usually sell for around, 900-1,400g If you get even 6 Vermilion Onyx, you already made your gold back.
I then take all of the green gems, and before I turn them into disenchanting materials, I check the Auction house for the blue rings and necks (Yes they still sell amazingly).
I stay away from Band of Blood, just because you can make more gold off of the Vermilion if you use them to Transmute.
I usually check the AH to see which rings and necks are selling for the best.
For
Rings on my server, it's:
Heart of the Earth
Lion'sfall Ring
Lord's Signey
Necks
Golembreaker Amulet
Skymage Circle
Widow Chain
Again, it's different on all servers you may need some experimenting before you can maximize the profit you can make.
After I'm done making the Blue rings and necks, I use the left over green uncut gems, and make the green necks and rings to disenchant.
Simply Make the Ornate Band's and Shadowfire Necklace Send them to your Enchanter, Disenchant all of them.
Helpful Macro to use with Keyspam
/cast Disenchant
/use item:83793
/use item:83794
/use item:90904
/use item:90905
Tip: I Disenchant the Blue Ornate Bands, and Shadowfire Necklace's, just because they take way too long to sell.
After Disenchanting all of these, you may have a few Ethereal Shards, with maybe a stack or two of Mysterious Essence.
Tip: If you find yourself running out of Mysterious Essence, usually I have way more dust than I need, and just make them with 5x Spirit Dust
I use an Addon Called
Auctionator to simplify this next step.
Opening up the Enchanting Tab, I scroll Through each enchant slot (gloves,wrist, weapon..ect) and Hit the [AH] Button to quickly check the price of it.
Maxing the Most expensive Item from the enchanting slot.
Ex.
Enchant Gloves - Superior Mastery - 300g
Enchant Gloves - Expertise - 150g
I usually make Two of the higher cost Enchant, and one of the lower at first just to be sure I can have all the enchants in the book that sell well, so there is a more variety.
Make all of the Enchants, If you have extra mats just go back and make more of those enchants to have back up's for when those sell on the ah, you can repost more instead of repeating this whole process again.
Tip: Don't be afraid to buy Ethereal Shards!
I Never used up my Mysterious Essence to make Ethereal Shards. Why? - Just a complete Waste.
Say if Ethereal Shards are going for 80g on your server, and Enchant Weapon - Windsong is on the ah for 350g.
Spend 80g for the shard
350-80=270 Profit.
Just be smart when buying the Shards, say if Blurred Speed is selling for 150g.
Enchant Boots - Blurred Speed - 2x Ethereal Shard
80x2= 160
160-150= -10g.
Seems like common sense, but just beware.
I also usually stay away from Enchant Weapon - Colossus, because it just takes too many Ethereal Shards.
Enchant Weapon - Windsong Takes 1 Shard, While Colossus takes 3 say again they're 80g each selling for 350g ( Usual on my server)
Spend 240g buying shards.
350*3=1,050g
1,050-240g=810g.
Say Colossus sells for 800, you're still making 10 less gold, and that is really high for on my server, they usually go around 500g
Doing this for a long time, creating ~10x of each enchant and just bulking up on everything to re-post them when they sell has made me at least 5k a day.
Here are some photo's of the most I've made in 1-2 days camping the ah and just reposting/undercutting.
Tip: EASY way to repost and undercut, you download the addon called
Auctionator you can go into more options and make it so that everything that you post is undercut by 1c. After posting everything, you can go to the more tab and hit check auctions and with a X next to the auction means it has been undercut. A check means, you are the lowest price.
To Wrap it up, usually with the other blue gems that I have, I usually Cut some of them, but usually sell them mostly uncut just because they sell a lot faster.
6k When I first Started this (Being a noob and posting the rare necks

)
https://i.imgur.com/5PgaM.jpg
19k in Two Days
https://i.imgur.com/Fm40F.jpg
27k In Two Days
https://i.imgur.com/MaKQY.jpg
TL;DR?
Prospect Gems
Transmute Primal Diamonds>Cut>sell
Make the green gems into some blue rings/necks use the rest to make the ornate bands/shadowfire neckalaces.
DE the Green Rings/Necks
Use the Mats to make Enchanting Scrolls