okay, I'll probably mess up, before I get an answer. The stupid tutorial has you choose a profession BEFORE you can see what people are trading for.
Of the two raw materials necessary, you can choose mining, or your professions specialty. (IE, weapon maker can learn either mining or carpentry, armorer has mining or leather, jeweler has either mining or gems).
I can't decide if its better to be a miner (and thus have items that I can sell to anybody, but have to buy all the specialized materials); or be a specialist, (and get specialist materials only some people are interested, and have to buy all the basic stuff).
It really depends on how much is available on the market- did everybody pick specialist skills, so its hard to get the basic stuff, or did more people pick mining, and the specialist stuff is hard to find/expensive?