Sydney is a multicultural city with food choices for every taste. Most popular theme seems to be water, everything from Sydney Harbour to the many beaches (Bondi the most popular) attracts visitors. There are a good verity of markets in most parts of the city and lots of fashion shopping. Interesting architecture new and old, including convict. Some old buildings have a uniquely Australian history and a slow walk around the city interspaced with coffee and snaks is rewarding. If golf is you, no...
An exciting country with great people. Leave lots of time, just to see the most popular Wats requires 10 or 12 days and as it is quite hot some rest time may be necessary. Very inexpensive. While you are there help the local people by purchasing locally made products.
Dont miss the Angkor temples. There are many of them and to see them all would take weeks. Accomadation is not expensive and the people are fun loving and friendly. Just be careful crossing the roads in the city or town. Siem Reap has good restaurants and a great market. Phnom Pen is an exciting city also with good markets and good food and the usual and unusal sights. I love Cambodia and the people.
Sun sand (both beach and desert), plenty of open space if you like to see natural country or thriving cities if that is what you prefer. Night life can be full on or beautiful relaxed restaurants. In the north the Barrier Reef is a must see. Crocodiles are also exciting from a distance. Australia is a very large country so have a good idea where you want to explore.