It depends on what you want to do. I am on my 57th time through the game (feels like it anyway :P ), and now I just want to level. So taking the time for all of my characters to work on professions is going to cut into leveling time. So I usually just take the gathering professions on my main and work on the others at later levels.

It's usually not hard to farm mats off of the AH for tailoring and leatherworking. But I sometimes find a lack of herbs at certain levels so you'd have to run around whichever lowbie zones until you had enough mats to progress. But I would say tailoring is the easiest, as I had dropped it twice and gone from 1-300+ just by purchasing mats.

Now I am playing through again with QuestHelper and all I feel like doing is skinning. I'm too lazy to mine/herb even when it pops up close to me on the mini-map :sleeping: