Oh, further tips for new people:
Only the elemental, "regular" knuffels from Knuffeltropolis give

income; the others give you avatar items. At lvls 10, 20, 30, 40, etc. up to 100 the wild knuffels will give you a random Wild Knuffel clothing item.
The elemental knuffels will give you 1k

at each of those levels. But it takes them longer to level up because they require more xp.
But also they can dig for you, which gives you materials (keep them for quests or sell them in the marketplace for

) and sometimes also food or the special digging items which change once a year.
And digging with them also does give them a little more xp.