I've been investigating one of the suggestions left to me in a comment: find items that can be bought, re-worked into something else, then sold for a profit.
The results are going to disappoint you. Given the variable pricing of different servers, different factions, even different days, prices are just too variable to say: "Here are some items that can be bought low and crafted and resold, always."
Really, the best way to approach this kind of thing is on an individual level. I can say, with some authority, that there are very few instances where you will be able to reliably make a big profit by buying materials and crafting them into new items to sell for profit. There are some notable exceptions, aside from just hoping someone stupidly sells something for too low:
Rare Crafting Recipes. Yes, those blue and purple schematics, plans and patterns that you see selling for hundreds of gold. If you're really going to make it work, you need a rare crafting item. Everyone else can make the vendor recipes, and do, so even if you do find the materials for a good deal, the new item will be worth very little. Actually, it's often the case that the new item is worth LESS than the materials, because demand for raw materials tends to be higher than for individual items.
Okay, so let's say you have one of those rare patters, either bought (easiest), or found (pain in the #!@%$). I hope you did some research on what the item requires to be made, because you can get screwed here with a final product worth less than the materials. A good example that I am familiar with is shield spike recipes - these recipes sell for a lot. I almost never see the spikes themselves for sale, simply because so few people bother to farm or buy the recipe. The same holds true for other professions. If you see a recipe for sale, and notice that you rarely see that ITEM for sale, consider the market wide open. It does take some individual research, and you'll be out a chunk of change if you buy the recipe, but over time you stand to make it back and then some!
Really quickly, here are some little deals to keep an eye out for:
- Motes. Sometimes you can buy 10 motes for less than the 1 primal.
- Unworked Cloth, Ore: Sometimes you can find the raw form, work it into a bolt of cloth, fel iron, whatever, and sell it for a profit.
- Uncombined enchanting items: Anything that can be used individually, or turned into something else when you get 3 of them, 10 of them, etc.
- Alchemy ingredients to turn into potions
It's a small list, and I'm sorry for that. If you want me to add stuff, leave a comment and I'll add it. Unfortunately, if it were easy to turn a big profit from buying-crafting-reselling, the market would be flooded with those items, and so balance itself out.
