Find a big second hand shop near you and stock up on summer stuff before you go. You don’t need perfect clothes for the trip and what you will likely wear in the hot and humid weather up North is not what you would necessarily have in your wardrobe on a day to day basis. I found a QuickSilver wetsuit in great condition for $18 at Savers in Noarlunga. You can save a heap of money and get what you need this way.