I played some Knack's Quest earlier. I got over 2 million points in a single run of Endless, so you can definitely get a lot of stuff. Sadly, all I got were Aqua, Amethyst, crystal, and Sunstone relics.
If people are farming crystals, shoudl we all add each other as friends on PSN? If your friends are playing too, when you open a chest that your friend opened you can choose their item if you prefer it over yours. If we all had like 5-10 friends farming crystals, it should be easy to get the ones we want.