Best thing to do is take every class to 15. And the best way to do that is just do every recipe once. The guild shop will always sell what you need to do that. Except for cooking. You have to buy the fish at the Hayline (sp?) which isn't far.

Also some of the things you make will be levequrst items. check with the levemete in town before you dump or sell anything.

Bonus. If you take the crafting armor rewards from the class quests and wear them you will have a fair bit of L1 crafting materia when you get finished.