Honestly, I'd say start with around 8-10 bottles first, then see how many you actually need, semua orang's situation berbeza! A few of us tried buying too many different sizes upfront and ended up with so many yang tak guna, so maybe stick with one size (usually 240ml for newborns works fine) and gradually add more if needed. Babies grow fast and their needs change, so better to buy as you go rather than stock up for 6 months sekaligus, you might find they prefer certain bottle shapes or teats anyway, yang is very personal for each baby!