Hi Leanne,
Picking up the camper in Christchurch and then bouncing around for a month is perfect. You're gonna have the time of your life, great time of year to go too. Really, it all depends on what floats your boat. What sort of things interest you the most? This will have a great bearing on what to squeeze in to that month.
Personally, I'd spend a little more time in the south island where your main decision will be whether or not to go around the bottom - along the southern scenic route OR cut through the Mackenzie Country, the great lakes and head inland. Both options have their merits - great merits. Going coastal you'll potentially miss the great lakes & Mt Cook, going inland you'll miss Dunedin, the Catlin's & Stewart Island. Move quick enough however and you could do it all, though quality time is really what you need here, the place is tooooo amazing to flash past.
Give us an idea of your interests and we'll see what we can come up with. For now and off the top of my head I'd have to say the South Island must do's would be:
The Fiordland
The west coast (glaciers)
Kaikoura
Banks Peninsula (just south of Christchurch)
Queenstown & surrounds
The great lakes (Tekapo, Pukaki, Ohau)
Marlborough Sounds
And the North Island:
Bay of Islands
Cape Reinga
Taupo
Tongariro
Rotorua
Bay of plenty and the Coromandel region
This will all make it tight on your time and of course, there's so much more to see, but NZ is a doddle to get around (compared to Australia) so I don't think you'll go far wrong having the time of your lives..
