Easy Wyvern Scales and Experience
Once you are at level 13 or higher with sufficiently powerful gear, head to the Hissing Wastes. Work your way to the oasis, located near the far west side of the map. Kill the enemies you find there and gather the wyvern scales, which you can sell for around 4000G for about 10 minutes' worth of work. It's a great way to gain both gold and experience points.