best place?

Well, if you like big places with lots of people and endless things to do, any of the main cities will have to do for you, such as Sydney, Melbourne or even Brisbane. I personally recommend the Gold Coast, you'll be always bound to have some great vacations around there.

i am in india . i have no idea about australia.

you may see Great Barrier Reef.

There are so many tourist destinations, you'll need to fit time and distances. You can get some good deals, just shop around a bit. Sydney can take a while to see, I'm still finding places, 26 years after moving here. I see you're from India, so you could start from Perth, via Adelaide, Melbourne, Canberra to Sydney, and you can then get anywhere else in Australia from Sydney. Domestic flights are pretty reliable, so if you want to go outback it's reasonably straightforward, and services are usually good. All of these cities have a lot of tourist attractions, WA alone could take a year to explore. It's easy enough to get around the country by air, moving at your own preferred speed. You could easily add Darwin on the way back, and stop off in Singapore. Enjoy!

I really dreamed to see the great barrier reef because it is one of the largest reef ever exist in this world and it is very spectacular to see even in the pictures. I wish i could be there at least i can relax.