I doubt that employers would select candidates who don't yet have a visa to live and work in Australia, unless the job advert mentions something about employer sponsorship being available.
Its quite common for job interviews to be done using Skype, so your location doesn't really matter.
Be careful about "moving to Sydney" on a tourist visa. If you turn up at Sydney Airport with all your luggage, no return ticket, any paperwork in your luggage which may indicate that you are looking for work etc, you may end up getting put on the next flight back to where you came from, and a 3 year ban on any further entry to Australia.
First things first - Are you eligible for a visa? What is your occupation?
Its probably best to consult a registered migration agent. There are several agents who participate in these forums. There is also an "Ask an agent" section in the forums. Perhaps PM one of the agents to get a professional view of your strategy?