A calculated risk is a chance you take after considering the outcome and an unnecessary chance is a pointless risk that is taken that could be avoided
This is really an opinion thing. But say Jay Gatsby, because he knows how to have a fun time.
I think its an Idiom. I don't see like or as. So no simile. I don't see he is something like a marshmallow. - No metaphor. I also don't see a non-human thing doing human things- the grass was dancing in the wind. My answer would be an idiom.
Hope this helps!
