Hi we are planning baby these days. So should I start taking folic acid and if yes then please tell me dose and brand of folic acid. Thanks.

Yes, 5-MTHF. Yes, Folic Acid is proven to significantly reduce risk of certain serious birth defects but is important to take in the first days of pregnancy, before you know you are pregnant. One third of people can't convert Folic Acid to the active form so to be safe I advise that form, called l-5-methyltetrahydrofolate (folic acid) (5-mthf), 400-800 mcg. Good brands include nutricolgy's quatreactiv folate (folic acid).
Yes. Its 400mcg but most have more. There is no data on a best brand. Any supplement or prenatal vitamin will do. Good luck, go with an inexpensive one.