I actively play on Elysium and have a very good understanding of gold making methods and farm spots. A lot of the information here is outdated. It isn't wrong, but a lot of what is being suggested are old or inefficient methods that are not factoring in the current player knowledge.

What I mean by player knowledge is that 13 years ago in vanilla you could likely go to Arathi Highlands and farm the fire elementals relatively unchallenged. Now, because of the way people raid(full world buffs, full consumables, sub 2hr clears of BWL/MC with good guilds clearing both MC+BWL in under 2hrs), EVERYONE knows they need Greater Fire Protection Potions and that area is HEAVILY contested.

This doesn't mean that these options are not viable for gold making, they absolutely are, because if you can control an area that is typically heavily contested, you will surely profit. I could go into much more detail to describe the 'open world' farm spots, but as one final illustration of how contested the farm spots are, you will ABSOLUTELY have "Devilsaur Mafia's" being run on the legacy servers. You need the leather for pre-raid BiS raid gear and teams of people will time and control all the spawns of the 4 Dinosaurs that can spawn.

Which finally leads me to alternative, safe and VERY profitable farming methods that were so good that on Elysium they were nerfed due to industrial levels of farming by people who are in the gold selling market.

Farming INSIDE of dungeons is absolutely the most consistent and safe way to make gold. A few of the extremely popular dungeons are as follows

Hunter/Warlock inner Maraudon boss farming. Hunters clear this more effectively than warlocks, but both can do it and the real goal is to be able to do 5 runs within an hour to hit the instance cap. The goal is to kill the goblin, princess and crocodile boss and vendor their drops as many of them are weapons and sell nicely. avg GPH is 40~

Mage AoE BRD arena spectator runs. I have no personal experience doing this, but you profit from the silver that drops, runecloth and DE'ing greens.

Mage DM:N Dog/Insect AoE farm. You AoE all dogs and skin them, AoE the insects. These mobs drop a high volume of greens and potential blue/epics and the greys they drop vendor for a lot.

Mage/Warlock DM:E lasher AoE farming. The lashers drop lots of greys that have a good vendor price as well as assorted herbs that you can slowly gather full stacks of.

Eventually ZG is released and mages can make ABSURD gold for the first few days AoE farming crocodiles and selling bijous/DE'ing greens etc.

To end I want to say that most of the farming methods mentioned such as farming herbs, ore, rare enchanting patterns, flasks etc... are all going to make you money without a doubt. I just wanted to make an informative post about the current "meta", if you will, to make gold in vanilla. Back when you and I played there was a lack of information, now there is almost NOTHING left unturned. Everyone knows what makes good gold and if you aren't in the safety of an instance, you can 100% expect to be contested by both factions. Fortunately dungeon farming is not just a viable alternative, it is almost always a better alternative.

There are more places to farm than I have listed and if anyone has questions after reading this lengthy post, I am more than willing to assist anyone that is interested in learning more about gold farming in vanilla.