Hi Luisa,
I don't think it's so easy since everyone has a different taste. I personally think, if it should be classy, it should have a metal case and a nice leather band.
But I have no idea what "not too small" means. For my wrist it's larger 48mm in diameter, but maybe your wrist is a little bit more girly.
So in my view, the size depends on the width of your wrist and the width of the watchband depends on the height of your wrist.
Then you have to decide for a case form: square, rectangular, tonneau, round. And for the color of the case, which depends on your skin color and maybe your hair color.
So, to help you further, maybe you can add some more details.
Best regards,
Alex