IMO, buying and selling items through the GE is the easiest way to make money. You don't have to be online while you wait for your offers to complete. You can spend 5 minutes in the morning setting your offers, and updating them after you get back from school/work, and just keep doing it over and over. The GE is so much better than any AH on any other game, because you cannot see other offers. This prevents undercutting and makes trading through it so much more profitable. If you perfect it, you can start building money towards expensive skills or discontinued items while you do whatever else on the game.
This is my method of making easy money on this game.