How do I apply for Chinese tourist visa and what will be cost ?

Considering your itinerary, you should apply for a multiple entry China visa which can be applied from the Chinese Visa Application Service Centre (CVASC) in Melbourne with these documents:
1. Original passport with at least two blank visa pages and a photocopy of the information page. Your passport should be valid for at least 9 months;
2. One completed Visa Application Form affixed with a recently-taken colored passport photo ;
3. tour ininerary
4. If you have not been to mainland China, provide copies of other ID, e.g. previous passport, driver license, etc; if you have been granted Chinese visa before, provide copies of recent Chinese visa with entry record