If you level your main combat class before a crafting class, you'll most likely have to rely on inferior quest rewards or random dungeon drops for gear (or buy it off the Market Board). I leveled my crafting classes before my main class and was able to take the cash reward from every sidequest afterward because I could make my own equipment. To have the relevant materials, though, you'll need at least both of your gathering classes leveled up beyond your crafting classes (or else you'll be buying materials).

It depends on how into crafting you really WANT to be, because it's not integral to any part of the main story and some people forego crafting completely, seeing as at endgame - the focus of most people - superior gear is given away like candy on halloween. Not only is the best crafted stuff expensive to make, it also takes a HUGE time investment to gather the materials, leveling other classes for all the cross class skills, and spiritbonding and overmelding your crafting gear to even be able to ATTEMPT the best stuff.

There's a certain pride to being able to do and make HQ stuff other can't, and at this point, all we can do is hope that crafting becomes relevant in the future somehow.