How or where do I get crystals for the Crystal Shop? I know I can buy them from other users but there must be another way?

THIS is the place you're looking for. You simply frag items in your inventory and they spit out a random amount of crystals depending on their rarities (special, holiday or similar rarities don't count here). The rarer the item the more crystals you're getting. I remember seeing a list that tells you how much crystals per rarity you can expect, but I don't seem to find it. o3o

Nvm found it here.

Hope that helped!

Thank you for both links. :)