While leveling I came across resource nodes as early as level 2! Not having a Mining pick was a real bummer, so I ran to the first place I could find with farming tools.
As soon as you have completed a quest that gives you one of the three tools (you will find one after the first instanced questline), go buy the other two tools from a vendor. I purchased Copper Harvesting Sickle and Copper Logging Axe, while picking up the Copper Mining Pick from that quest I mentioned earlier. For humans I believe it was the quest where you help out on the farm killing worms, feeding cattle, and watering corn.
Once you have your tools, go out there and continue questing, but this time you'll be gathering valuable resources to sell on the Trading Post!
Also purchase Crude Salvage Kits if you can afford them. These are used to turn your discarded blue gear into valuable crafting materials.