Truegold is not a item that is farmed it is a item that is created by alchemists but in order for alchemiests to be able to create truegold you'll need some materials whch we can farm.
First you will need
10 volatile air
10 volatile water
10 volatile fire
3 pyrium bars
First for volatile air we will be heading over to uldum to farm the air because it has the best drop rate we know for volatile air and here is the location for you guys.
Now for the other 3 materials needed we will be heading over to twilight highlands because the best drop rates for the 3 other items needed are in twilight
volatile water we will be killing elementals this is a easy task for any character
for pyrium ore you can follow this route planned out for you you will need to make 3 pyrium bars.
farming for pyrite can be a long task.
in order to make the pyrium ore into pyrium bars you'll need a miner
Volatile Fire this is the location for you guys if this one is over farmed the you can always head over to mount hyjal just outside the entrance to firelands is also another good gathering places for volatile fire