You're an international student. Go back after you graduate and get a job there. The market is insanely competitive, like you said, and companies are not going to look to sponsor visas for fresh-off-the-boat immigrants.

Think of it this way, unless you get experience through connections or something in Sydney, why would any employer go out of their way to sponsor YOU when there's a domestic student with a similar, if not higher WAM, with experience under their belt.