It doesn't really matter what you pick since all the crafts have their niche. Make sure you take up a relevant gathering class for it too (ie: Botanist for Carpenter, Miner for blacksmith, etc).

As long as you sell things at a reasonable price, you can make some significant profits and help out fellow newbies. A good rule of thumb is to check out Mooglebox.com to see if there's any NPCs that sell what you're planning to make, and price below them. I try to sell items for 1k x the required equip level, so a level 10 gear for 10k, but you can try selling for a lower/higher amount depending on how demand and what you think is a fair price. Some items are more difficult to get ahold of the materials for, so I charge more for them.

As far as what craft to pick, make it something that will benefit whatever battle class you plan on playing. Right now, Alchemy, Cooking, and Goldsmithing are a little lacking because they are relying on revamps that are coming next patch, so I'd say to avoid those for the time being. Actually, I'd still get Alchemy to 10 just for Preserve since it's a really useful ability =P