Attempting my first guide here, not promising it to be good.
So a great way to make gold is through fishing even at low levels.
Right from lvl 10 if you get your fishing high enough you can fish deviant fish in the barrens, which can sell anywhere from 2 - 30g a stack (depends on server)
Then from lvl 20 - 30 it gets a bit dry, but after that the money hits with stv.
I am currently playing a druid (now lvl 46 but been doing this since lvl 30)
with the right fishing levels you can pick up stacks of oily blackmouths and firefin snappers (believe these to be used in alch). The oily tend to go low but the firefin snappers sell 3 - 5g a stack (depending on server)
But the biggest money maker of all is the ship wreakage piles (something with wreak in the name). I fish these all the times for fishing skill, they drop chest.
In those chest I often get green every 3/5 chest. Which sell for awesome prices (had one blue also).
There are ways to make the money come faster also, weather it be aqua form, a swim speed belt, a mount, and so on.
Also if you fish enough you should get the book to track fishing nodes (Amazing for fishing in outlands and it shows the wreakage you'll be looking for!)
^^Have not fished up another book and did not check if soulbound, if not it might sell well.
I got class so thats the most I can give at the moment, hope you all like my first try at a guide/idea on how to make money.
(P.S stick to the western shoreline, the eastern tends to be dry of fish)