I plan on a low budget, mainly walking around, public transport, and inexpensive meals (if thats possible)… Which Im learning is not.

I plan to visit Sydney for a few days, fly to Adelaide and stay for a day or two, rent a car to Alice Springs, stopping at Coober Pedy and Ularu. From Alice Springs, fly to Melbourne for a few days stay and then back home. If logistics (flights and car rental) are fixed, where can I expect and also avoid cost? What do you do to save beside camping? Whats your advice driving the Stuart Highway? In a Toyota Yaris?