B-12, calcium and iron are standard :) Make sure the B-12 is the dissolveable methly type, and a liquid iron if you can.
Though, I'd take a good multi-vitamin on top of that just to make sure. Garden of Life is supposed to be the best, as is a brand called New Chapter. Though because I'm a poor student, I take a multi by Nature's Way called Alive! Energizer and it's pretty good and costs under $15. I get the iron free version because I take a more absorbable liquid iron. Tablet irons aren't well absorbed by the body.