Level 20 and just left tortage? One of the first things you will want to do is go pick up your gathering quests. There is decent xp in gathering and the sooner you get it the better because as you level and fight different mobs, some of those mobs will drop items you need to collect for your gathering quests.
Start by picking up the gathering quests in the Purple Lotus Swamp, or Potain or Lacheish Plains. Visit the various NPC's in the cities there and start the quests. You can do all them at once unlike crafting which is completely different and will only allow you to have two different crafts. You can gather in mining, prospecting, skinning, stonecutting,weaving and woodcutting. Turn each one in as you complete them to the trainer to get the next level of that quest. There are level restrictions to gathering as well so it is meant to be done as you progress through the levels in your own character.
Certain items from gathering are selling quite well on the trader as well and your guild can always use collected items to progress further in the building of the guild city. We will list the items that we are curently looking for on the MOTD in game.