Should I purchase some cash before arriving into New Zealand?

Getting New Zealand Currency before you leave
It is a good idea bring a small amount of New Zealand Currency with you, so you don't need to spend time organising cash at the airport or at the bank on your first day. Your local bank may need to order New Zealand Currency so allow a few days for this in your trip preparation. If you for some reason are not able to get any currency before you come, all major kiosks at the airport should be able to help you.

Exchanging cash as you travel in New Zealand
You won't need a lot of cash at once, as exchanging cash in New Zealand is easy. Just get enough to cover small purchases on your first day, such as a cup of coffee or lunch. When you do need New Zealand Currency, any branch of a major bank including ASB, ANZ, BNZ, Westpac or Kiwibank will have the latest conversion rates, which are consistent throughout the country.

Carrying large amounts of cash while you travel In New Zealand
New Zealand has one of the highest credit card and eftpos usages in the world, so there is no need to carry large amounts of cash. Most retailers including traders at local markets and convenience stores accept electronic payments. This means you will be able to pay for virtually anything with your debit or credit card as you move around - and this is also the safest and most secure way to cover your expenses while you are in New Zealand.