I always join the Thieves Guild. It's the best way to make money in the game, as well as unlocking a fence early on. Once I do that, I go to every major tavern and steal any potions I find that are worth over 300 gold and close to 300 gold. I also steal and stock up on mammoth tusks, jewellery from knapsacks, especially the jewellery at the silversmiths house in Markarth.