Professions for making gold
If you are just looking for the best profession to make gold in classic WoW, the Gathering Professions will most likely be the right choice for you. The easiest combinations are Skinning/Mining or Skinning/Herbalism. Especially while leveling, Skinning is amazing because you will kill lots of beasts to skin anyway, so it’s very time efficient. If you pick up Skinning early on, you will not have any problems leveling it up because of this, too. Another good option is Herbalism/Alchemy, which can be good even at lower levels. That is, if you can keep your Alchemy skill up to date. Some potions like the Free Action Potion can be crafted quite early and can sell for some nice gold.
If you don’t want to spend too much time on you professions though, you might want to consider Skinning, and switch it out for Alchemy once you hit level 60. It’s similar with Mining/Blacksmithing or Mining/Engineering, although there are fewer things that are profitable at low levels for them. In addition, it takes more time to keep Mining at a skill level where you can mine everything in the zones that you level in. It can be worth it though.
While we are at it, we might as well get this out of the way. The most useful profession by far for PvP is Engineering. There are so many useful tools and gadgets that can save your life in a fight that it’s almost a must if you want to compete with the best. You have grenades for extra damage and CC, a chance for a ress without being a healer class, and so many other tools. As for your second profession of choice, you might take Mining to make it less expensive to level up. Or you could get a Crafting Profession to make yourself some gear.
Cloth and DPS
While Engineering can also be good for PvE to get a small damage boost for DPS classes, there are some other ones that need to be mentioned! For example, there is a cloth set in Zul’Gurub, the Bloodvine Garb, that requires Tailoring skill in order to wear it. This set is great for Warlocks, which makes Tailoring a great choice for Warlocks. Even for other cloth wearing classes, Tailoring can be very good. This is because there are some unique epic items that Tailors can craft and only wear themselves, like the Robes of the Void, or the Truefaith Vestments. A good choice to get along with Tailoring is Enchanting, as these two professions don’t need materials from any of the gathering Professions.
Having covered cloth wearers, rogues, hunters and druids commonly go for Skinning/Leatherworking. This is a great combo, due to the Devilsaur Set, which is pre-raid best in slot for some classes.
If you are a Warrior, Blacksmithing is the one for you. Especially if you want to tank, you need to get the best gear possible. So becoming an Armorsmith is almost mandatory for Tanks in the top guilds, and even for DPS, Weaponsmith is also a great choice.
In conclusion, if you are looking for the best Professions to make gold, the gathering Professions are the best for that. Other than that, it is mostly the best to get a Profession with which you can craft equipment for yourself. So that you can wear it. Engineering of course being the exception for this.