With so many potential farming locations to choose from, it's worth trying out a few different approaches without devoting too many hours to them at first to get a sense of what you find the most convenient, most enjoyable, and most profitable.

For those of you who have gathering professions, an addon such as GatherMate will almost certainly make it much easier to ensure that you never miss an herb or a mining node. In order to make gathering easier and more efficient, GatherMate will remember the location of every herb and ore you collect, and will display that information on both the mini-map and the world map at the same time.

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Gathering is a good way to start earning money right away. Simply seek out resources to gather or mine while leveling up your character, especially if you are skilled in skinning and leatherworking. Make a mental note that you will not be able to pass the 225 skill mark in your professions until you have reached the level of 35.
One important point to remember is that you should always sell your gathered items at the auction house, and you should use your bank alts to make the process as efficient as possible. In addition, you should look for long-term buyers for the mats; they are out there – just ask in the chat and keep your eyes peeled for them in the trade chat room. This will ensure that your sales remain consistent while also saving you the time required to place mats on the AH.
Farming is more suitable for characters with a higher level of experience (level 40-50+). Generally, farming revolves around instance runs, killing named bosses multiple times, running dungeons repeatedly in order to increase the chance of getting a desired drop, and farming mobs in various locations and areas.
Dungeons and Dragons
It goes without saying that the requirements of a perfect grinding spot are best met inside dungeons, where no outside interference is possible, and where you can be assured of receiving full respawns instantly each time the dungeon is reset. The only restriction is that you can only run a total of 5 individual dungeon lockouts per hour before the game will no longer allow you to create new instances of the dungeon, so make sure to plan your time accordingly.
Turn the Auction House Around
Buying an item at auction and reselling it for a higher price results in a profit for you if you do so successfully. If you are skilled at flipping Auction House items, you can make a substantial amount of World of Warcraft gold in a relatively short period of time.
For this reason, it is preferable for you to spend every day scanning the auction house, using some buy WOW TBC gold addons to determine the current price of enchanting materials at low prices (such as "strange dust"), and then checking the prices of the green items that people post for sale, which generate dust when they are disenchanted. The Enchantrix mod will display the best guess for each disenchantment that you have. This method can be a convenient way to obtain World of Warcraft gold.
Various occupations
Professions are extremely important in WoW Classic, as they play a significant role in both earning money and providing much-needed items towards the end of the game. It is therefore recommended that you learn them as soon as possible, regardless of your intentions.
One of the quickest and most straightforward ways to earn additional gold is to learn some gathering professions as soon as possible – any two of the following: Mining, Herbalism, and Skinning.