According to the forums, you are guaranteed the first two avatars, so two keys. You can do it with 2 cat cafes, but you can also do it with the two new parties. It is a 2 week hunt and only need 500 tanks for 1 key. Not sure about the other avatars. I think it is random with mixed in gifts, but it is two weeks, so I think you can do it within the 2 weeks that the hunt lasts.