Elite Challenge Event Farming guide

You get 17 crystal first time you completed the Elite Challenge and the objectives.

2 for completing the Elite Challenge

5 for completing each objectives

You will also get a free 5 Star Marco after the first time you completed the 10th stage.

It is recommended that you complete at least 10 stages.

(Stage 10 Rec. Lv. 65, Rec. Prof. 30 )

It is really time consuming to finish the elite challenge everyday, so I would recommend doing it just once for the crystals and then see if there is a particular souls in the shop that you really want to get, and aim for it.