The most unforgettable thing about Sydney is the beautiful sunset. Sydney's sky is so clear so if you sit down at the beach around the sunset time, you would feel like you are in the heaven.
Quick Tips: If you want to save money in hotels, I'd like to recommend YMCA. It is very clean and convenient, and even has family room.
Best Way To Get Around: Sydney's transportation system is great. You can go anywhere by bus or ferry. If you have strong legs, I'd recommend you walk around the city as there are so many street cafes and small shops.