dream cruise suggestions

I am the recipient of 2 tickets to fly *free* almost anywhere in the world and want to plan a "dream" cruise...I would love some suggestions :)

I am thinking to fly into one continent, say Europe or Australia, cruise to another continent on a one way cruise, then take another one way cruise back to either North America, then fly home.

My criteria are that the total prices of the cruises don't exceed $2000- 3000 per person ... and that I am not gone for more than 30 days total.

(waiting to book a few months prior to departure will save us $$ and we are fine with an inside cabin) ...I just need some suggestions on good routes that other cruisers have taken...

thanks for the help in planning :)

sorry, I posted this is the wrong forum. I need to figure out how to move it or delete it.

Circumnavigate Australia. Doing it. 27 Feb 2015 on Princess. 28 days. 2 days to get there and one day home. You need a minimum of 32 days though