Kate

Pretty straight forward,

Use a few crystal-makers to produce Jade.

The when you've got 100+ in your pocket, head to the desert salesman on a Sunday and buy 100+ stair cases.

Lastly, wait until this quest comes up, camp in the desert by the cave entrance and at 0600 head into the cave.

Use your staircases until the challenge is completed in one go - don't bother battling, mining etc unless necessary