Gold in World of Warcraft: Classic can be earned with a bit of luck too. By killing and looting mobs you might find some truly rare items. Some of them might be usable by you but others might not. Don’t just sell that piece of rare equipment to the nearest vendor as it can earn you quite a bit in the auction house. Especially if it’s an item for a level 50+ character.
And for talent builds. I prefer to make my own talent builds. But I've been playing RPGs since the 8bit days so half the fun is building my own characters up. I already made and bookmarked 1 deep fire mage build, 2 elemental mage builds, and 2 deep frost mage builds. And I might remake them tomorrow if I read up on any good talent choices I left out my 1st 5 times lol. And I have multiple builds for the other classes I play too.

You will need initial funds to start this way. Buy for cheap and sell for actual price or higher – that sounds pretty easy. But you should have basic knowledge of prices and always track the market. People use to sell for cheap when they need fast gold or don’t know real value of the item. So, it’s your chance to act. If you see anyone selling an item for low price in trade channel, contact them immediately. You should use all of your trade skills to negotiate about the price to make it as low as possible. It’s important ability to communicate. Besides, it’s good to get addons to trade effectively on Auction House: Aux or Auctioneer. They allow you to scan auction, compare prices, find cheapest options, post items quickly, and many other useful tools. It is possible to make your first thousand out of ten gold you have in a pocket.
Mobs out in the open world generally have higher movement speed and higher attack speed than you. If you were to stand still and trade hits with a mob back and forth you may end up trading 1 of your Auto attacks for 2+ of theirs. If executed properly, The Hamstring Method allows you to trade 1 hit for 1 hit with a target, drastically reducing your damage taken while not reducing your damage at all since you are monitoring your natural auto attacks with the swing timer.