Sydney is a nice city plenty to do and see. I recommend the harbour bridge, the opera house. Vivid is good to if your around Sydney end of May. The hop on hop of boat is good. You can see lots of parts of Sydney and visit there zoo also. The blue mountains is a nice place to visit you can do trips from Sydney to visit there or it's a 2hour train ride for $8.80. Sydney is the most expensive place so far that I've visited. Goon is cheap it's a boxed wine. Get some lemonade though!
Insider Tip:Coles is a cheaper supermarket compared to the 7/11 convience stores. Bondi beach is beautiful and is only 7$ return on the bus but you have to prepay for the buses. You can get this from the 7/11 shops.