Folic acid is essential to prevent spina bifida.
Just take supermarket prenatal multivitamin.
Don't take non pregnancy ones as they sometimes contain animal derived vitamin A which is dangerous if pregnant.
Lots of pregnant women also become deficient in iron and calcium so look out for them on packs.
But dont take iron with tea as it reduces absorption. It's best with orange juice/ something high in vitamin c.
But it's best to see what foods have these nutrients in them and eat more of them as you'll absorb them better from food than pills
Eg spinach, steak, lamb, mince, cheese, milk, cream, yoghurt, broccoli, kale, wholemeal bread, eggs. Fortified cereals are also good.