I think better ambil 0-3m and 3-6m. NB size tak muat tu. If baby you 2.5kg ke bawah, NB size tu okay. Boleh pakai lama. Anak I lahir 2.4kg at 37 weeks. Pakai NB size for 2 months. Banyak mana nak beli tu depends on you. My experience dulu I beli mixed sizes yang cukup untuk seminggu sekali je basuh. Sebab husband I did laundry on his off day.