The baseline for gold farming in this game is farming raw mats. This is better done on a level 50 character with maxed crafting for Blacksmith, Woodworking, Clothing, and jewelry crafting, but it can really be done at any level. For those four mat types, half of your mats will be at your character level, and half will be at your crafting level. High level mats are worth more, but both can be refined to produce tempers such as Alloy or Dreugh Wax. Alchemy doesnt distinguish, so it can be done at any level. If you are gonna farm, farm everything IMO. Basically, pick a zone, pick a direction, and pick up everything you see. Refine, sell, and repeat. This can certainly produce 50-60k an hour, if not more. Make sure you have a source of major expedition, and if possible, enough CP to unlock the gatherer passive (or whatever its called).

The reason I call this the baseline is that prices in this game tend to reflect this. What I mean is if it takes you on average 1 hour to farm a specific item, the price will generally be at least in the ballpark of what you can make simply mat farming for that specific amount of time. If there is skill involved (motif farming in vet dungeons for example) you will usually get a bit better bang for your buck in terms of efficiency.

The are a few other things that are worth farming, and everyone has their preference.

-Stealing/pickpocketing can also be a pretty steady source of gold, as NPCs can drop a wide range of items. Not my personal favorite, but it is steady gold.

-Item farming, should be at CP 160 to do this, otherwise you are wasting your time. For example, Mother's Sorrow (drops in deshaan) is the FOTM for magic DPS in PVE. Farming treasure chests or dolmens can drop items that you can turn around and sell. If you get an inferno staff in the right trait, you can sell for 300-400k. Good trait armor is fetching in the 20-30s, and jewelry is around 15k. There are certainly other examples, but it takes a bit of market knowledge and knowing what is currently the FOTM.

-Motif Farming, either from certain vet dungeons or the latest DLC, can also be quite profitable. I would advise against farming motifs that have been in the game a long while

-Plunder farming. Get a trial group, and try to speed run trials. You get plunder that sells to a vendor. Takes a group, but you often see "plunder runs" in zone.

-Furnishing plan/recipe farming. Find a place with a lot of cabinets, dressers, etc, and loot away. Traitors Vault in Summerset is the go to place this patch.

2 Other very good things to mention.

CRAFTING WRITS: IMO, there is no better steady source of gold and materials in this game. They do take some leg work to get several characters ready to do them, but once you do, they give you everything you need to play the game. I make 40-50k gold in about 30 minutes just from turning in the quests on 8-10 toons a day. That doesnt even scratch the surface, as its a great source of gold mats, master writs, surverys, repair kits, soul gems, alchemy mats, etc.

Writs are how I make my money in this game. I have stacks of every gold mat, and have well into 8 figures of gold. I do nothing else to make money. It is not a get rich quick scheme, but it is one of the most efficient things you can do for 30 minutes a day if you are in it for the long haul.

Flipping Items: If you want to get stupid rich, you flip items. Go from trader to trader, buy low, sell high. It takes capital and market knowledge, but it is probably the fastest way to simply acquire gold.