We got given some flannelette cot sheets so we use them and since most of his clothes are secondhand we have some long onsies that are too big so if it's a freezing night he wears a singlet, socks and maybe a thin longsleeved tshirt and tights under that. Makes changing him a pain! But also keeps him toasty since our windows don't close all the way and it's a high rise house so it gets FREEZING already