Good morning Ladies,
It does depend how your baby grows etc. My Son wore Newborn up until around 6 weeks. Then 0-3 Months for around 8 weeks after that. I found that he was on par with his age pretty much and from around 3 or 3 and a half months he would go up to 3-6 Months clothing and so on. Only when he turned 1 did he start to wear clothes for longer periods. He is 3 years and 2 months old now and still wears 2-3 Year pants, but 3-4 Year shirts and tops fit him well.
Also different shops make different sizes. Like Woolies and Jet tends to be smaller than Edgars. Nappies I have no idea and cannot remember. I have bought 2 packs of each size and will just buy as I need from there on.
My Son had a bit of eczema and still does on his cheeks, especially in winter. I couldn't use Johnson and Johnson or Elizabeth Anne products on him. The nurse at Dischem suggested I buy plain old Sunlight baby soap and I still use it to this day. I used that to wash his hair when he was a baby as well. It is so mild and wonderful for sensitive skins. I can also recommend Sunlight baby washing powder for their clothes. That's the blue box.