Although this can probably be done in various places, I found the following to be the easiest.
What you will need/want:
-Squire Energy Potions
-Dwarf Squire
-Waterbreathing Rune
-Muuk Bow (Max Level)
-Magic Rune (optional)
Now, select the Zafira Faris stage to initiate the Al Sharaf Desert level. Select Epic difficulty to increase money potential.
At the start of the level, make sure you have Muuk Bow and Dwarf Squire selected. Now use a Squire Energy Potion to level him up. Hold down 'X' to quick fire and begin working up a combo to get as much money as you can.
When you reach the sand whirlpool section (with the sandworm enemies) you can travel down if you have the Waterbreathing Rune.
Shortly into this section, there will be lots of sandworm enemies that make trails of sand blocks. Each block will count towards your combo meter. When the screen fills up with blocks, use the 'A' button to unleash arrows in 5 directions. Each arrow will completely tear through any and all blocks in its way. This will drastically increase your combo meter.
Shortly into the above mentioned section, there will be two treasure chests. With the difficulty, squire and high combo, the contents should net you approximately 3000.
The boss (Ifrit) awarded me around 1000. All you have to do is acquire an additional 1000+ from regular enemies along the way. This shouldn't be too tough using the above method.
Note: The optional Magic Rune is listed because it will allow you to use more Muuk Bow shots and help you keep/increase your combo meter.