Beyond calcium, the three I'd say are worth thinking about are iron, omega-3 (DHA specifically), and making sure your general vitamin levels are topped up, iron helps with energy since breastfeeding already drains you quite a bit, and DHA is important because your baby is getting their omega-3s entirely from you during this period. A lot of mums I know just continue their prenatal vitamins after delivery since most of them already cover calcium, iron, and omega-3 together, which saves you from juggling multiple supplements. That said, some find the iron in prenatals causes constipation, so it's worth checking with your gynae or a dietitian whether you need to adjust the dosage or switch brands. If you prefer food sources, cold-water fish, chia seeds, and walnuts are decent for omega-3, though the consensus seems to be that diet alone is hard to rely on consistently when you're already so tired and busy. Honestly, I'd weigh whether a good all-in-one postnatal supplement makes more sense for your lifestyle versus piecing things together individually.