On the one hand, you can sell your not-wanted items in Auction House (AH), and other players can buy them with gold. On the other hand, if you’re ever browsing the Auction House and you see an item cheaper than usual

The best professions for material farming include Mining and Herbalism (with Fishing serving as a solid secondary choice), as you can mindlessly traverse the world searching for different nodes

Go to Steamwheedle Port in Tanaris and fish the shoreline/dock in this area. Don’t free fish! You want to fish directly from pools. Run up and down the coast and check for any Stonescale Eel pools.

Farming is more suitable for higher level characters (level 40-50+). Farming works around instance runs, killing named bosses multiple times, running dungeons again and again for the chance of getting

You can check seeking prices with NPC merchants using addons like Vendor Pice. You will, in fact, find that addons will be quite worthwhile throughout the game