I don't think there is any need to wait until you're 25 - I honestly think it would be realistic to set a goal of flying First class to Asia within the next 12 months!
As others have said, I would be seriously looking at buying United miles. Join the United Mileage Club program now, then wait for a 100% bonus miles promotion. These promos are actually pretty regular - every few months or so another one comes around.
At a 100% bonus, you could buy enough United miles for a return First class ticket from Australia to Asia on Thai Airways for just USD1400. Then you'd be looking at just a little extra to cover the taxes when redeeming the miles. Doing this, you could realistically fly to Bangkok or Hong Kong for $2,000 return, or just $1,000 one-way. IMHO that's a very achievable goal for the next 12 months.