As a fan of Calvino I will say that If on a Winter’s Night a Traveller is somewhat more enjoyable after you've read a bunch of other Calvino, since it has a somewhat cheeky, self-referential feel and the more you sympathize with the author the more you may like it.
Numbers in the Dark is very good as a place to start.
Marcovaldo, Cosmicomics, Difficult Loves are my favorite. Baron in the Trees too.
I'd definitely suggest starting with these. His short story work is beautiful.