Instructions
Repeat quests that give good rewards, such as Nightbane's Castle. Quests that require you to clear out an instance will usually result in a variety of awards, in both monetary support and experience points.
Sell the rewards from any quests you complete. It may be tempting to hold onto a piece of gear that you will be able to use on another character, but selling the gear can provide for the character you are playing at the present time. These items are usually worth money and can cure even the lowest of bank balances.
Sell the loot of any monsters you kill. Nearly any monster you kill can drop an item that you can in turn sell. Take the time to pick up every item that drops and sell it to a merchant, as opposed to just leaving it on the ground.