Conflict of interest warning: I am a co-founder of Lightning Pay Limited.
Decentralised / Private sale (Advanced)
These methods are not for newcomers, but recommended as they provide more privacy than the other options.
NZ Bitcoin Only Brokers
Brokers are companies that buy the crypto on your behalf and send it to you. This makes the process easier but they charge a fee that is usually included in the price they charge for the crypto.
Buy Bitcoin in NZ with Lightning Pay (recommended)
NZ Bitcoin Only Exchanges
Exchanges are the market where buying and selling happens, you can likely get a better rate than on the broker but the buying process can be a little more complicated
International Exchanges & Altcoin Brokers
International exchanges often have more volume for a better price