If you are going to take a crafting skill, unless you already have a 70 on the same server, for the love of God, don't take a crafting skill unless you also take that crafting skill's gathering profession, OR, if you have a friend who is willing to supply you.
For your first character on a server, it will be VERY long and arduous to level a crafting skill without its gathering skill. For example, Blacksmithing can take well over 5,000g to get to 375, without mining your own ore. Even if you DO mine your own ore, it STILL takes a longass time to level Blacksmithing.
That, and most crafts are simply useless for actual money gain until way later in the game. I can think of nothing in Blacksmithing that will net you an actual profit until Outlands, and even then it is questionable. Alchemy is a bit of an exception to the rule; I've sold potions for Profit now and then (Gift of Arthas, Magic Resistance Potions, Mana Potions, Some of the Buff Potions, etc), and Alchemy is cheap and easy to level anyways.
Of all the crafting skills, if you are going to craft, do Herb+Alchemy. If you are leveling a character on a new server, the best thing you can possibly do, is go Mining+Herbalism. Herbalism won't make you much from the get-go (mining will, however), but it will start to shine after you get to Briarthorn (and the Swiftthistle you get from Briarthorn plants) and then when you start getting into things like Sungrass, Mountain Silversage, Gromsblood, Purple Lotus, Arthas' Tears, etc. Most of these go for 1g+ per herb, and the later zones are covered with these herbs. Heck, Black Lotus goes for a whopping 10g on my server.
Once you get to 70, if you really wanna craft, THEN is the time to start crafting. You can do dailies for 10-15g a pop (which will buy you a lot of mats early on) and provides you with the money to ply your trade, instead of having to farm for hours upon hours upon hours.
Speaking as a Warrior, Blacksmithing never allowed me to make anything worthwhile that actually helped my leveling career, and as a Lv25 Rogue, only 2-3 leather recipes were actually worth it (not including the first couple white armors <Lv10). I think the only two crafts that helped me level, were Alchemy (buff/mana/hp potions) and Engineering on a Hunter (guns and scopes. Mainly the scopes).
With Enchanting, as a Lv70, you will make your life MUCH easier by waiting until 70, when you can solo many of the earlier instances for your mats. One instance run can yield several BoP Blues which DE into nice things, and whatever you can't get ahold of, doing dailies will get you the money to get ahold of them.
So, no matter how you roll the dice, it is always more profitable and easier to wait until you are 70 before you do any crafting, unless it is Alchemy for any class, and Engineering for a Hunter.