Nearly everything that drops off enemies and harvestables are either useful in crafting or will earn you favor. As a new player make sure to use the "Small Talk" option with every new NPC you discover to learn about their likes and dislikes. Experiment by giving them appropriate gifts. This will give you over time an idea of what's worth holding onto. If you don't know what still are not sure or want to hold onto stacks of items to do with an itemgift later, store it with Hulon and start buying additional vault slots. You will be happy to have those stacks of items many levels later when you realize what they are for.