well from what i remember (and its been awhile before i paid attention) this is the format.
Regular knuffels from Knufftropolis:
Every 10 levels gets you 1k FPs
Leveling up in one element will make it easier to dig for items on Candy Island.
Digging will get you Materials (which you can use for Quests) and FPs (currency)
Digging will also get you Dig Items (which are yearly updated exclusive items you can only get from digging. They're usually avatar items. Most recent items
are here)
If you level up a knuffel to its corresponding element (eg. leveling up Water for a Water Knuffel), you will get less EXP when digging. On the other hand, if you level up a knuffel in any other element (eg. leveling up in Earth for a Water Knuffel), you'll receive more EXP.
Donating a regular knuffel BACK to the shop will get you 1k per each level (in other words, if your knuffel is level 100, you'll get 10k back)
Wild Knuffels:
These are knuffels created by users on the site
Every 10 levels, you'll get a chance to "roll" for a Wild Knuffel item (avatar items inspired by the Wild Knuffel designs. The items I sent you were Wild Knuffel items)
Wild knuffels can NOT dig on Candy Island