You could go to Primary Gathering Master in Carefree and Wu Long Village to learn and upgrade Gathering Skill. Find vegetables in the map to collect. You will get some collecting EXP while carrying on your work. Gathering cost you certain MP. When your EXP is full, system will remind you to upgrade your skill, and it requires certain amount of money. When you're qualified, you could go to the advanced collecting master to learn higher level collecting skill. Vegetable is essential material for cooking. Gathering prepares materials for Cooking and Manufacture Cloth Armor.