Ds was born mid dec and he lived in nappies and singlets. Most days i put a sleeveless and body suit (snap crotch thingy) on over the singlet. At night we wore the same with a muslin wrap and socks. We had the fan on in the room and the a/c going in the house most of the time.

Put it this way, you dont need much. I do remember having a couple of longer all in ones JIC and i did need to use them as we did have a few cooler days over christmas