To make your gold , one way is to buy low and sell high. You will need an initial investment. I suggest at least 10 gold if not 50 - 100 gold. But, 10 gold will get you started.many players will watch the trade channel in their main city. They watch for WTS (wanting to sell) [item]. Players selling like this want to sell their item now and not wait for AH - this is the perfect opportunity for the low/high buying player. You simply send them a private message asking how much or by saying I will give you x gold for that item. From there, you negotiate. The idea is that you try to get the item as low as possible. Make sure you always buy lower than it can sell for - this means watching the auction house like a hawk. You have to know what is worth what and how quickly it sells. Supply vs. Demand.
three things to note:
First - other people will see the rise in price in that market and decide to start selling the item as well. If too many people do this, which ALWAYS happens, abandon the market - sell what you have left for more than you bought it for and be done with it. A way to identify if there is too much supply is if there are 20+ of that same item at the auction house. So, you will be controlling a market for roughly 2 - 3 weeks before you move on to another market due to increase in supply.
Secondly - people will NOT like you for doing this. In America ,this is considered illegal. You ARE monopolizing a market and giving people no choice but to buy from you. You will get a negative reputation if you do this long enough - especially if you stay in a market for too long. So, you may not necessarily do this with your main character.
One Last Thing - this method eats up a lot of time. You will have to check the auction house at least twice a day to make sure everything is fine and at your price. You may end up doing this over leveling even. So, only go for this method if you want a challenge. Remember, you cannot just buyout all of a market and expect the worth to change in one day - it takes at least a week of monitoring.
A note to those trying to fight the monopolizers - if they are doing it correctly, you can't beat them by selling for less. Instead, sell for more. If the price of an item goes too high, then the market will crash. Suddenly, the prices will be within reason again. You can force this by having a base price at a price you think it should be and a buyout higher than what the monopolizer is selling for. This way, someone gets the item for the right price OR the monopolizer must buy the item at a loss. There you go; there is your ammo for fighting the fight.