As far as I am aware (we are both self employed our whole working lives) super is optional if you are self employed. (You don't have to pay yourself super)
Gst is only chargeable/payable if you are turning over in excess of $75k
You may find that it is not worth dealing with gst if you don't have a heap to claim.
It's a PITA to do.
You would only nee to take out GST if you are charging it.