It worths to collect from your purple cow, it sometimes drops gem.
Shibuya, I was also thinking on a new quest about adventure-only items. I dont think they have a limit like crafted materials, but we can point a number like 100 each. I also have many anvils, scrarecows, pumpkins, campfires etc., from the overgrown bench (also adventure-only bench) I found like 30 pieces, most of the are in front of my animals.
So what do you think of a new quest of every adv-only items?
(including the new ones from the envoy to the plume)