The bottom right hand corner of OZ is a quite diverse place, compared to the rest of the continent that is.
Picking up a campervan in Adelaide and hitting the road you should head for Mt Barker, then Strathalbyn (sort of south east) then head to Meningie via Wellington. This has you heading along the coast alongside the Coorong, which is a long skinny wetland between the road the the sea. You can actually drive a car along the beach legally.
From Kingston in SA you could possibly leave the coast behind for a while and head to Naracoorte. There are caves there and one of them is called the Fossil cave, it is a huge repository of fossils which I believe will take another 60 odd years to catalogue. The public tours are fascinating and I believe the research is carried out by Flinders University. Otherwise head to Mt Gambier.
However if you did go to Naracoorte, keep heading almost due east to Edenhope and then in the general direction of The Grampians which is a huge national park, the town for supplies is either Horsham (Nth) or Halls Gap (in the Grampians).
From the Grampians where you will see lots of real Australia before the white man came and farmed it, head sth for Warrnambool via Penshurst. From here you pick up the best parts of the Great Ocean Road. Follow the coast from here via Port Campbell where the 12 Apostles are and various other good sights. Note the waves hit the mainland directly from Antarctica here every 14 seconds and erode about 50mm of mainland every year. It is possible in winter, which is when you will be here, to see 30 metre waves hitting the mainland as you look down from about 50 metres high. Pretty awe inspiring I can tell you. Plus the thudding of the water has to be felt to be believed. The best place for seeing these waves is shortly before Port Cambell after Peterborough.
From Apollo Bay onwards the place becomes quite touristy, but still reasonable.
I would suggest you head for Queenscliff, which is south of Geelong. From there you catch the ferry which is on the hour daily each way to Portsea. You may see dolphins as you cross the heads of Port Phillip Bay.
I would then in a roundabout fashion head to Wilsons Promontory. This is the southernmost part of the mainland and is one of the few parts of the mainland in this part of the country to be more or less as it has been for thousands of years, great place.
From there think about heading up to the Snowy mountains via a great road. Head to Bairnsdale for supplies then to Buchan, interesting cave there as well, but not as good as Naracoorte. from Buchan you head up Barry Way, through quite small places like Butchers Ridge, Wulgulmerang and Seldom Seen. Then shortly after that you hit the NSW border. From then on for a while you are travelling alongside the Snowy River and there are quite a few camping places virtually on the river. One or two of these places have a pit toilet, saves digging.
From there and after travelling through 75 Klm's of winding road through virgin natural forest, you will be in Jindabyne.
From there you can head for the coast again, or take a side detour to Kosciuszko Ntl park, nice, or continue up through ACT (where Canberra is) and then take back roads to the Blue Mtns behind Sydney. In the Blue Mtns you can organise all sorts of things depending on the weather.
The Jenolan caves not far from Katoomba are quite spectacular.
Whilst hugging the coast is a good idea, you will get a far better experience of some of the interesting things available, by heading inland at times. Apart from that, constant coast can become a bit of a bore, sort of like us travelling through Europe, not another bloody masterpiece".
I can fill you in on quite a lot of this area as I have travelled very extensively throughout it over the last 40 + years.
You'll need a tripod almost anywhere near the southern coastline with a biggish camera, the wind is sometimes quite strong
Mick.