Cooking gives you access to a unique consumable type that usually sells pretty well. Let’s look at the top recipes in phase 1.
The selection of buff food is a little lackluster this phase. For the most part the only food we get access to is the types that give a boost to stamina and spirit. This is useful, but generally speaking players pay more to do damage than survive. The one extra option is the Smoked Sagefish, which does give mana per 5 seconds. This is useful for healers mostly.
For stamina there is a ton of options. There are some +8 foods available, but only one recipe you can reliably get on the AH. Heavy Crocolisk Stew is one option, and the Tasty Lion Steak from the alliance quest in Hillsbrad is another. For +6 my best suggestion is the Goblin Deviled Clams. These are very cheap, and the clam meat is very abundant as players farm the clams for Iridescent pearls. On top of that these are also used in crate turn-ins, so you are double dipping.
If you are a rogue then Thistle Tea needs to be on your radar. I made so much gold selling this in classic. A lot of rogues don’t want to bother with cooking or spending time crafting the tea. I made an absolute ton of gold with this recipe, and you can too. It can even be worth leveling a rogue just to get this on an alt. You get it from the level 20 class quest, so it does take a bit of work, but it will be worth it as this recipe is relevant for the literal entirety of classic.
Below you can find my cooking specific group. I only included the +8 variants mentioned as well as the clams. If you prefer any other recipe in the same category, just swap them in and remove the ones you don’t want.