The fact of the matter is that there is not enough time in the day to make use of every available option to make gold in the game. As more and more doors open up, you will find that you simply can't do it all, no matter how much you play or how well you plan ahead. As you advance more into gold making, you will find that there are certain activities which are just not worth your time. Players like to determine what is and what isn't worth their time using Gold per Hour, or GPH.
For example, let's take mining. If you can collect 20 stacks of Ghost Iron Ore in half an hour, and they sell for 60g a stack, then you've made 1,200 gold at a rate of 2,400 Gold per Hour. This method works well for tasks such as farming, be it for raw materials, such as gold or items, or any other relatively simple task. It gets a bit trickier when you're talking about mass production of items. If you spend half an hour to re-list auctions, craft new items, and post the new items, and then you don...