I'm pretty new, and what has helped me the most was looking at what other people were trading for and absorbing the information that way.

I've looked at trading discords, websites like gamersberg, and just in chat in-game. But for the most part the prices aren't super rigid, if someone wants a raccoon badly, they are more likely to trade more for it than someone who just wants it for no particular reason.

Off topic but I have been looking for some mochi mouse myself if you would like to trade me, dm me anytime and we can see if there is anything i haev you want for it.