Always turn in HQ items for GC provisioning daily, use survival manuals whenever you can, use gathering food, try to stick to evaluation leves if your gear is good enough to always get the bonus. The other leves offer decent exp as well, and of course you can mine things that you know you need/ will need for something else.

Personally I didn't mess with leves until about 30, and at that point it was kind of half regular gathering/ half leves until 40 or 45 when it was almost entirely exp through leves. I was in no big hurry though.