You can start crafting right away, but what is going to stop you is having the skill points you need to invest so that you can craft higher level stuff. Skill points will be precious while your getting your character to L50.
What you can do in the meantime to level crafting is decon everything you get (Runes, Armor and Weapons). That will level your crafting with no points invested. Also, research Traits, knowing Traits lets you make special crafted sets. This can take more than a year to learn them all. But you can be making decent stuff in two weeks and really good gear in less than two months if you do your trait research right.
While leveling to 50, just use Mob loot for your gear, it will take care of you just fine.
Alchemy and Provisioning you can level in less than an hour, so don't worry about those.
Listen to Nestor. Hands down that's the best thing to do when you are just starting with the game. If you want I have a ton of crafting guides on youtube, with a directory here on the forums, if you want to see about each craft.