When you're wandering around and see an item on the ground that you think might be valuable, pick it up and try to sell it to the appropriate vendor. Make this a habit and before long, you might end up with a lot of gold.

You can use talismans, wands and scrolls, and anyone but Battleragers can use potions. Figure out what all of the ones sold in cities do and determine which might be useful to you. Also, there are shopkeepers in some guilds in major cities that sell really useful items. One of these will make ranking a LOT easier for you in early to mid levels. A hint: for necromancers, there is a talisman sold in a major city once you hit hero range that can make you a lot more powerful.