Kmart brand terry onesies are bigger than the other brands
non terry onsies are bigger than terry ones.
Bonds make great leggings for boys or girls, but there are other brands out there in unisex colours too now.
some people cut the toes out of their terry suits too to stretch their life, i've never done it though 'cause i've always planed to keep them for next bub.

I have red tights for my dd, and I think red is pretty unisex. but you should be able to get navy tights or white tights.
Bonds do a knee high sock now but I think they are girly colours only.

leg warmers would be good too, lots of different brands out there