I was in Adelaide visiting a friend last Dec/Jan. I'm not sure about the accomodation but you can of course check out hostelworld.com and such for the prices. It's important to know where exactly do you want to visit in Adelaide cos when I went there I thought Adelaide being a smaller city compared to Syd and Melb, there aren't much to do; and I was there to just spend time with a friend. But turns out there are quite a few things to do. For one, Adelaide Hills will be a good start since it's a decent distance away from the city; you can do a day trip there or spent a night if you want to. There are a few areas to visit in Adelaide Hills, but I just managed to drop by Hahndorf (a German village) and nearby is the Strawberry Farm of the famous Beerenberg jam. You can pick strawberries there which I did

Other than that, if you're into wine you can always visit the wine valleys, e.g. Barossa Valley, Jacob's Creek and many more. You should also google more about the Fleurieu Peninsula which covers places like Victor Harbour and a few other interesting spots. If you like to see wildlife at closer distance and see them at their natural habitat, then you should go to Kangaroo Island which is kind of like a open safari. But it's difficult to travel around cos there's no public transportation there, (truly nature at its best), so you'd either follow a tour or rent a car.

The city itself has nothing much to offer really, since KL has way more shopping malls. The usual one that the locals go to would be the Rundle Mall. You should also try out the Haigh's chocolate that Ade is famous for and if you're curious on how they were made, you can always go for a tour in their choc factory. Not a lot to see but it can be a relaxing afternoon tour around. Oh, and they have the Botanical Garden in the city and of course museums and there's a famous lake as well, but I can't quite remember what is it called.

Hopefully my experiences can be helpful to you...

I'm not sure of the exact amount I spent there. Minus the flights I think it was about 700 AUD. But I was living with a friend, so accommodation was free and cos I went for a tour that - I realized was quite exp after thinking about it - costed 400AUD for 2days 1night in Kangaroo Island. In total, I spent 1100 AUD for 15 days for both Ade(11days) and Syd(4days). I was on my own in Syd.

For meals, you can get kebabs for 6,7, or 8 aud. A proper restaurant meal would be 15-20aud. The bus system in Ade is kinda efficient. If you will be staying more than 3 days in the city, I would recommend that you buy a one week pass rather than paying everytime you get on board the bus cos it's cheaper. You can get the weekly pass from the Adelaide Metro office in the city (just ask anyone, they'll know).

So how much you need depends on what kinda trips will you be going. I think 1 week will be enough to cover the South Australia region unless you wanna take it easy and it'll be good to bring about 700aud.