There are hundreds of camp spots along the path you want to take, and different way's to get from Sydney to Melbourne. It would depend on how much you want to rough it, If you want to stay very close to civilisation and by the ocean, I would look into staying at camp sites near these cities and towns. They are very easy to get to and within a few hours apart. But In my opinion, The best spots are just inland from the coast, great ocean views and you get that alone in the bush feeling, even though your 30mins away from the coast.
Here are just a couple of spots that I can rattle off the top of my head that are between Sydney, the Victorian Border.
*South Sydney - Royal National Park
*Kangaroo Valley - Bendeela camp ground
*Nowra - Yalwal camp ground
Moruya - Wyanbene Cave camp ground
Eden - Ben Boyd National park
* are close to where I live, I'll be happy to be a lazy tour guide, I can show you the hidden treasure's your after.
I will work for beer.