Breastfeeding: Carters

Advice for Sizes in a Children Store

I want to open a children store reselling brands such as carters, oshkosh, little me, etc. The store would be in Colombia so I dont worry for the competition but I really have no Idea how to buy like how many of each size, diversity etc. My store will be from newborns to 24 months. I also want to include small accessories like bottles, breastfeeding stuff and small toys.