I’m from NZ as well, defiantly head to Queenstown/Wanaka. They both have lots of accommodation options, you can stay at a backpackers for around $25 a night and I think they will give you a cheap deal if you stay for a while. Wanaka is sweet coz you’re real close to snow park, Cardrona, and treble cone. Snow park is a big terrain park, so its got all your jibs and jumps and Cardrona is just a good all round mountain + its got a sweet park as well now. Treble cone has epic backcountry and lift accessed terrain. So you have a bit of everything, and Queenstown’s not too far away either, with coronet peak and the Remarkables. Basically you wont find more good quality resorts all packed in so closely anywhere else in the country, so if you choose Wanaka or Queenstown you will be sorted, there the best options in the country.
best months to go would be August and September
There are also sum fun little fields throughout Canterbury which can be epic on a powder day so keep that in mind