My dd was born in mid-November and I am Brisbane but we still had about three wondersuits/long sleepsuits for her and they definitely got used.
Mostly though she wore short sleeved/short legged suits. But in NSW I think it would still be fairly cool (esp at night) in October so I would definitely invest in some cotton long suits.
My bub is due end of October as well so I'm basically planning to do the above as that's what I ended up doing last time