First-time attending a Western wedding, what should I wear?

Hi, I'm from Indonesia and I have been invited to a wedding of my close friend in Australia. This is my first time attending a wedding in a Western country and I'm not sure what should I wear. Should I wear a tuxedo or can I wear my national costume? In Indonesia, people usually just wear t-shirts or jeans because the reception is attended by hundreds of people and is usually done at one's house. But I don't think I can do that in Aussie.