Kites: Bring a 12-14m kite, 9-10 and a 5-6m if you can. You'll probably get to use them all over the course of a month of travelling.
The water around the South Island can be cold so make sure you have a good wetsuit, booties, a cap and even wetsuit gloves.
North Island - Auckland
This is a short guide from a New Zealand kitesurfer.
South Island - The lakes
Cold as glacial bodies of water, 4/3 wetsuit country but they get good afternoon thermals (coming down the Alps towards the plains). Big winds in the famous NW'ers too. Pack a small kite.
Coleridge is good but cold, can be a little gusty.
Lake Clearwater is a smaller, shallower and thus warmer lake in the Ashburton group and can be very good.
Wanaka and Wakatipu lakes can be good but launching, wind funnels and gusts can be a pain.
Aviemore in the Waitaki valley can get really consistent in the summer months for Arvo thermals.
South Island - East Coast
Christchurch area is the pick with a regular cold Easterly seabreeze, 15-20 knots most settled days. The Estuary became a giant oxidation pond in the earthquakes and while it's a good flatwater spot it's slimy and muddy underfoot.
New Brighton beach offers miles of onshore wave type sailing on an open beach, just stay away from the pier and popular swimming spots.
Further North Waikuku beach and the Ashley river mouth lagoon offer awesome kiting. 3/2 wetsuits in the summer.
Coast South of Christchurch
Dunedin Middle Beach (Moana Rua)
South Island - West Coast
Plenty of swell but not really that great for wind. The mountains are right on the coast and keep the winds relatively light even in a howling onshore, a SW seabreeze can set-up which provides some side to side off kiting around Westport at Carters Beach but to be honest I'd just enjoy the scenery or go surfing.
South Island - Nelson area
Fairly consistent N-NE seabreeze depending on the prevailing weather patterns. Only around 15 knots so you will be on big kites but the spots and consistent winds make up for it. Occasional nuking SW comes down the valley too.
Spots here are Tahunanui in town, crowded by NZ standards but has an emptying estuary "Magic carpet" so get's a good 5 knot boost on wind speed. It can get choppy. It's a cool beach though because you can get a coffee at the launch site, easy rigging and launch areas.
Marahau is about an hours drive away and the gateway to the Abel Tasman National Park. Huge sand flat and at mid tide has sandbars to jump, shallow clear water and channels in between. This is probably the most unforgettable place to kite surf in NZ, amazing scenery, golden sand and super fun kiting. Gets around 15-17 knots in the seabreeze. Usually 4 or 5 kiters out when it's on.
Golden bay is a giant shallow bay and sand flats, loads of spots and gets way more wind than the Nelson side of Takaka hill- happy hunting over there.
Enjoy but be prepared to kite alone!