All I know is that Scribes are going to make bank with those Contracts. All guides talks about them and everyone will want them. Better ride that money wave while we can. Other than that, Alchemy and Jewelcrafting are always safe bets with tradable and marketable goods. Engineers can get an item for followers to bring back more Azerite, ot sure how much of a headstart that's gonna give them. The rest of the professions honestly looks kinda lame since most of everything is BoP anyway.
Honestly TL:DR of any guide. Is learn your markets, it's as simple as that. Learn who's in it, learn what's profitable, watch different time tables. I've earned 2 million profit OFF 1 market and half set up TSM. I've barely tried before this I was a hardcore raider, only made gold over the years through BOE farming and run sales (which are goood, don't get me wrong) but I want to be making the multiple gold capped characters.
Patch 5.3, like all new updates, is attracting a throng of returning players, many of which will be undergeared and willing to spend Gold to catch up with the rest. While the profits might not be as lucrative as with the new items, there may be less competition here. The key here is scanning the market for in-demand leveling gear and producing the right amount to avoid getting stuck with an unsellable stack of outdated items.
Recipe ranks basically make you more efficient at making stuff, either by letting you craft the same number of items for fewer materials or getting a higher yield from the same amount of materials. As an example, having a one-star rank recipe lets you craft items at a relatively inefficient way, but when you acquire two-star or even three-star recipes, it can almost feel like you are crafting items out of thin air because of the low amount of materials required for each craft.

As with Jewelcrafting, Alchemy is a bit more nuanced than looking at hourly rates. Flasks will provide you with a good baseline, but if you carefully watch the market and plan your transmutes with market trends, you could see huge gains like JC. Assuming you are focusing only on selling Flasks, you will make around 2138 gold/hour if you are also an Herbalist.

The Company protects the privacy and integrity of the data it collects by employing appropriate administrative protocols, technical safeguards, and physical security controls designed to limit access, detect and prevent the unauthorized access, improper disclosure, alteration, or destruction of the data under its control. The Company transmits the data used by its external service providers for the specific outsourced operations listed above across public and private networks via recognized encryption technologies, such as by using Secure Sockets layer (SSL) software, which encrypts the data you input.
Thanks for all the information! I’m between jobs atm so I only had enough money to get a month (haven’t played since legion launched) so I’ve been stressing about trying to somehow build my gold up to buy game time instead of enjoying it. I’ve had a lot of fun just trying to catch up on my Demon Hunter (maxed his level and am about to start the Mage Tower stuff and work towards reputation for allied races) and when it gets tedious, I’ll switch over to my engineer and craft stuff or level my new character I’m going to use for herbalism and alchemy. Hopefully when life is a bit steadier and my WoW standings improve, I can use all of this advice to make some $!

In a few months only mats will be worth anything. At this point we have people with tens of millions of gold and people with just a few thousands. A flask takes tons of mats to make, and they will sell for well over 10k gold each, so the casual players won't afford them. When people realize that the rich guys will always take buying from the AH over farming their own mats, the prices will go even higher, then casuals will notice how expensive flasks are, and they will pick up alchemy and make more flasks, driving the prices down again.