Which supplements to use after pregnancy?

I am a year post-partum now and this winter I noticed my skin was a
lot drier than usual, especially in the cuticle area. At my annual
physical a few months ago the doctor advised me to start taking a
multivitamin, plus calcium. I was overwhelmed by the choices at the
pharmacy as well as my Whole Foods store, and didn't get anything at
all.

It seems there's a whole science to food supplements, and I don't know
where to start.

What are you taking that you've found effective?