Folate is important.
The blood tests include iron levels. If you have low iron you need supplements but if your iron is fine don't bother. There is a liquid iron called Floradix. IMO it's way better than the tablets.
Calcium is important too but if you're eating lots of dairy then you probably don't need supplements.

I took one preggy vitamin a week just in case I was low on anything that I didn't know about.