Pildappa rock near Wudinna is a great low cost Bush camp.
Willow Springs Station and Skytrek are my top spots for the Flinders. Lots of great little camps on the Eyre peninsula, locks well can be windy though.
Lincoln Cove national Park, Coffin Bay national park and Whaler's Way are all worth a visit.
If you have time the museum at the visitors centre in Pt Augusta is well worth a visit.
Camping at mambray creek is better than staying in Port Augusta.
If you head into the Barossa, there is low cost camping at the Greenock oval with the pub a short walk for a nice meal. The Brewery, Kaleske Wines and Murray Street Vineyards are also stumbling distance away.
In the riverlands there is a free camp alongside the overland corner hotel, or on the waterfront not much further past there.
Big Bend further down stream is great too.
If you are looking for some Caravan Parks, the Kirton Point caravan park in Port Lincoln is the best one in the area.
The Whyalla Foreshore park is nice, but whyalla is a one night stop at best.
The Yorke Peninsula is pretty under rated and well worth a visit to Walaroo and surrounds as well as Port Vincent and surrounds, you could easily spend a couple of nights at each and only scratch the surface.