Luggage and bags:
Most likely large would be best for all the shopping and also to be prepared for all types of weather.
Clothing/Shoes/Weather Gear: Bring everything. You'll experience all four seasons in one day in Auckland. During summer, it can get quite hot, but if you're in the shade and its a little windy, then it will be cold. Then it might have a bit of a shower in the afternoon. So you could be going from shorts and singlet to a jump and umbrella. In the peak of summer however, you'll get stretches of a week or 2 of beautiful sunny weather. Even in winter we have bright clear blue sky days, but just cold.
Toiletries and Medical Supplies: Just you usual. Nothing special or extra needed.
Camping/Beach/Outdoor Gear: Bring a raincoat if you're coming in autumn or winter. Don't bother with camping in winter...it won't be fun. During summer its a great idea. Bring some hiking boots if you're into that.
Clothing/Shoes/Weather Gear: When going in Auckland in the spring, or for anywhere in NZ for that matter, be prepared for any kind of weather. When the sun is out in November, it's hot. When it's raining, it can be a deluge. It can also snow at higher elevations, and I experienced a morning run in thick frost while at Lake Taupo. Bring long sleeved shirts (synthetic or wool, to keep you warm), pants, warm socks and rain gear, as well as any summer clothes you hope to use when the sun does come out. And dress in layers if the weather looks iffy, so you can put on and take off clothes when needed. While in Auckland, a spring rainstorm would roll in out of nowhere and drench me to the bone in one minute, then the sun would come out shortly to blast me with heat and I would be steaming gently the next minute. Thank goodness for long- and short-sleeve Merino wool shirts (made in NZ, naturally), which are light and warm, and a good umbrella.
It rains quite alot in winter, so be prepared to get a little wet. Forget umbrellas, the wind is too strong to be carrying umbrellas, get raincoats instead
Toiletries and Medical Supplies: Like Australia, the UV rays in NZ is quite high, so it may be cloudy, but dont be fooled, better to slap on some sunscreen or carry a cap/hat.