The tools used by a cook are rolling pins, sifters, or a skillet. Double clicking one of these items will bring up a menu of all the kinds of items you can prepare, bake, or barbeque.
Water pitchers can be filled from the sea (at certain locations, i.e. off a bridge), water barrels, or water troughs (commonly found in stables).
Cooking can be done by any heat source, such as a campfire, a stove, an oven and a heating stand. Notice that the heating stand makes a nice accessory for the travelling cook as it can be carried anywhere.
Fish steaks are probably the best way to raise cooking skill. Fish a while, cut up the fish, then go to an oven and cook them one by one. You will need a pack animal to hold the stack of fish steaks and just take one out and put it in your pack at a time, otherwise you will cook all of them at the same time. Your skill will soar in a hurry, and it costs you nothing.
If you're looking for a quick buck, I suggest tailoring. If you're looking for a skill which can support itself after a fashion and which has a lot of variety in terms of the things you can make and the process whereby you make them, cooking may be for you. When you need some money, make bread, but be sure to refill your water pitcher rather than buying water. Or barbeque some raw chicken or fish steaks and sell them to other players or NPC's. A good way to turn your cooking skill into gold is to offer the creation of savage skin paint. Warriors that have been in battle with savages often come back with large amount of tribal berries. By combining these berries with flour, a skilled cook can create the desired paint.