Seeking advice and travel mates for my trip in Australia

I've been working in Australia for just over 4 months and will be finishing this job in September after which I will be going to Perth to visit a friend and prepare for my backpacking adventure. I have no travel mates yet and am absolutely winging it, I plan on visiting Melbourne, Sydney and Brisbane but plans could easily change what's more important is the memories I make and people I meet along the way. I'm posting here asking for any advice and trying to find people who may be road tripping near me and might let me join the ride.