You might want to check if your local public library subscribes to Ancestry Library Edition. This would give you access to the census records and other records that may be helpful, depending on the location of the ancestors.
Also, if you are near a Family History Center (the familysearch.org folks), they may carry a subscription to Find My Past and/or Ancestry Library Edition. You can see if a center is located near you on their website. I don't know off hand if there are any located in NZ.
As was previously mentioned, ALWAYS start with what you know for sure and work backwards from there one generation at a time. And keep track of where you get each piece of information from as you go along ... you might not be able to remember later when you want to find a particular record again.
Polarbear
