The reality is sucks, but unformatunately you can't change it. If it's your dream course you should fill out the applications as best you can.
Is there something you have done which isn't very impressive but you can make sound impressive? I think that's generally the key to winning at applications when you're too young to have actually had work experience. You were surely involved in something in school, could you bend it around to be at least somewhat relevant?
Also, do you have a language? I'm sure that would help.
Otherwise, if it doesn't work out, you could use the next 6 months to gain experience - travel, join an aid organisation or UNYA or something, write letters to people on Christmas Island, take a language TAFE course, start a blog about international politics, volunteer to teach English to people from other countries, that sort of thing. I assume you'd like to do stuff like that hence your interest in the course, and it would make you look good if you decide to try again.