How long are you planning to go there for? Is this just a short-term thing or are you looking to use a Working Holiday Visa to stay up to a year?
If it's just a short trip then I wouldn't recommend booking a tour.
If you're going for a long trip.....then I definitely wouldn't recommend a tour.
It's easy enough to sort stuff out when you get there and there's no need to pay someone an extra fee to sort it out for you, especially not from your home country.
That being said, if you did want some kind of tour that will give you a chance to experience a whole lot of different 'cultural' events and see the sights then I'd recommend the Oz Experience. http://www.ozexperience.com/
It's a hop on, hop off service so you can travel to a time that suits you and you won't be forced to drink all the time. The flexibility of the pass means that if you want to see more of a place then you can. Or if you really want to keep travelling with other people you can still see them on the way. It's up to you. An organised tour from home might not give you as much freedom
They provide accommodation on some of the longer trips (for example, at a sheep ranch) but generally you can book your own place in each town/city, as you like.
In reality though, you should be able to sort most of this stuff out for yourself with a bit of time, the internet and some hard work. Look at cheap airlines to travel around (Jetstar etc), buses between cities (Greyhound), which hostels / hotels you want to stay at (Booking.com / Hostelworld etc), read a guidebook about the sights and activities you can do in each place (Lonely Planet ;)) and talk to some other people who have been before.