What folic acid to start taking before trying for a baby?

According to the current PTG guidelines:

In all women of childbearing age who have a low risk of fetal defects and pregnancy complications, supplementation with folic acid preparations at a dose of 0.4 mg / day is recommended. In this case, folic acid is enough, e.g.
Folik: https://www.gdziepolek.pl/app/produkty/30782/folik-tabletki/apteki?

For women at increased risk of fetal defects and pregnancy complications, supplementation with a dose of 0.8 mg / day is recommended before at least 12 weeks before pregnancy. In this case, it is worth betting on better absorbed methylated-folic acid (folate), e.g. Naturell: https://www.gdziepolek.pl/app/produkty/98573/naturell-folian-tabletki/apteki

For women at high risk (explained in the table below), supplementation with 4 mg/day of folic acid is recommended at least 4 weeks before pregnancy. Here, too, it is worth taking folate.

The risk group to which you belong is determined by the doctor individually on the basis of the interview.

I also encourage you to read the article: https://www.gdziepolek.pl/artykuly/jak-przygotowac-sie-do-ciazy-w-10-krokach