Not much! I had a summer bub and all he lived in was singets and a nappy and a lightweight onsie at night. He only wore clothes when we went out somewhere. They aren't in 0000's for that long at all, so best to only have a few items that size and most in 000's, especially considering that summer could last well into April, but seeing as how you are in Melb, you may need some long onsies just in case you get a cold snap.