Container and to some extent, mob loot. So, open every single container you come across. Some Crypts are great for this, so are some Dwemer Ruins as they have a lot of Urns and other containers to loot.
But, your also going to get a bunch of lock picks and 0 Value Armor and Weapons too along with your other vendor trash.
Enjoy the game, life is what you really want to be worried about.
PakKat "Everything was going well, until I died"
Gary Gravestink "I am glad you died, I needed the help"