Beat the game to unlock hard mode, create a 55 monk, go farm. At that point there are many areas you can do.
You aren't going to make much gold until end game and you aren't going to have any farming builds until you get to the next to last or the last area and can cap the needed Elites. The only normal mode area that is worth farming is the Underworld or FoW and you aren't going to have access to those areas until late in the game, even then they are MUCH more profitable in Hard Mode.
Until then pick up all drops and sell them to the merchant or appropriate trader. From the Jungle on ID every item (it raises the sale price of whites by more than the cost of the kit at around that area) before it goes to the merchant. Do all the quests. To save money use collector armor/items - check the official wiki for a list of collectors and what they trade. Be careful purchasing runes, though they can be reliably salvaged from armor (don't bother with insignias until you get you final armor) so you will not loose that gold.
Lastly if you want a lot of money but your account perma-banned when Anet gets to you spot in their server logs go see the gold sellers. Other wise you are going to have to do the above.