Level a Gatherer or a crafter first

[Deleted]

level the gatherer first if you have :
a) little time
b) little effort avalible to spent on your proffession
=> relatively low amount of cash gained

Level a crafter first if you have:
a) lost of time: you need to be among the first at cap level or close to it to get the top level recepies.
b) lost of effort avaliable: you will need to know how to get the mats, how much they are worth, how much people are willing to pay for mats and end product.
c) lots of gold, or an other way to get your hands on lots of high level crafting materials
=> highest amount of gold gained

[vian]

From my experience, new herbs and ores are often alot cheaper the first few days when people level. Then they gradually go up and eventually down to their "set server price".

[Skarssen]

I would get the character you want to raid on leveled up first. There will be things you will want to get started on such as dungeons, faction rep, challenge modes, raid prep, etc., that will have some sort of gating effect, so get your lock to 90 first. Once you do that and are rolling on dailies and such then you can worry about his/her professions.

Also, if you are savvy with your crafting professions you will make far, far more gold per hour of time invested than you would via gathering. Gathering will be inefficient at first since there will be a lot of competition for nodes. A lot of people will be using gathering professions to make money, whereas the truly rich players won't be wasting time looking for nodes; they will be sitting in the AH turning profits that way. If you power level your crafting profession rather quickly you will have to pay a premium price for materials, true, but then you will have a market for crafted armor/enchants/glyphs ready to sell at exorbitant prices as well.

My advice, level the warlock and get him started on raid prep. Then, let the "blue collar" players do the gathering while you sit in the AH and rape players on crafted items.