It sounds like you are doing it correctly. You can level each of the crafting classes to about 15 without leaving the guild. After that you need either stuff that can be gathered or made by the other crafting classes.
Leves are the best way to make quick xp without having to worry about finding too many various materials. You will get back 6 leves per day. You will also want to try to make hq items as they give twice the rewards for leves.
To better your ability to make hq items, you will probably want to level several crafting classes and pick up some of the cross-class skills.
There is likely going to be a demand for more low level gear with the influx of ps4 players, so you can also try just making lots of copies of some low level gear. It won't level you particularly fast but you can hopefully make money off of it.

For the gathering classes, again leves are the best way to go. :/ Without the leves, just go for the highest level stuff you can.
Fishing is pretty easy since you can stockpile the fish and then turn them in when you have the leves.
Botanist works well with weaver, culinarian, and carpenter.
Miner works well with armorer, blacksmith, goldsmith, and alchemist.