One of the best farming areas for gold is act III, because of many big group of monsters, some very straight forward areas, some special caves with extra treasury goblins or resplendent chests.
We are doing our runs in Nightmare act III. There are 2 possibilities.
The long run (~1h 15min) starting quest: The Breaches Keep or the shorter one (~30min) starting quest: Siegebreaker. Both runs lasts until killing Azmodan.
In comparison of gold per hour they are very close, but the shorter seems to be better. I don't have enough time to make enough accurate tests.
A) starting quest: The Breaches Keep
I try to explore the hole map and killing as much monsters as possible. Sometimes you must travel a very long way back to explore all areas, but as a Demon Hunter with following skills we should not loose too much time. (Vault with Tumble, Preparation and Tactical Advantage)
If you explore all areas, then you will need about 1h 15 minutes.
With this gear (175% gf without Follower, Ferret Companion and Nephalem Valor Buff), 200.000 gold per hour is possible.
My current tracked record is 262.000 g / h with total 323% gf and 108% mf (224% gf and 33% mf on my own items). This run last 1 hour and 6 minutes.
I'm still working on improve my runs and many runs I don't track, because of this learning and improving process.
Theses gold values are from picked up gold + quest gold + gold from vendor for sold items.
Not including items, which are sold in the auction house. All items with no value for the auction house should be sold at the vendor.
B) starting quest: Siegebreaker
During your farm runs you come into the are Bridge of Korsik, there you can find the caverns of frost. Inside this cavern lev 2 there could be a named mob Chiltara. If you kill him, you will get the Gibbering Gemstone, which you need for crafting the Staff of Herding for the secret level.
next Part V - Farming Area II
DH Gold Find Guide - Introduction