Luggage and bags:
Mount Maunganui is located on the North Island of New Zealand and therefore your bag will need to contain fairly warm clothes for a July trip.
Clothing/Shoes/Weather Gear: I was comfortable in a windbreaker and jeans. Since I did do quite a bit of hiking, I may recommend a more athletic type attire for Mt. Maunganui specifically, but the city is very casual.
Toiletries and Medical Supplies: Readily available throughout Mt. Maunganui.