Being a small country the size of UK, with a small population, (4Mil), there are plenty of wild places. In two hours by car, from anywhere in the country, you can get to good hiking (tramping) areas. So outdoor activities are extremely popular, and equipment readily available.
Temperatures are relatively benign, but being between the tropics and the roaring forties the weather is extremely changeable at all seasons. So you have to be prepared for rain, gales, midges and even snow at any time of the year.
So the history is for bomb-proof but rather heavy gear.
Tracks, (trails) are much better now than they were say even 30 years ago. Main ones have plenty of huts, (I understand there is nearly 1000 public and private ones in the country) and the popular trips are well documented. One paperback I have is entitled "75 great NZ tramps" and it does not even include my favourites. But trips can range from easy to near impossible- just choose your own challenge.
Because of the weather and the rugged terrain, ultra-light equipment is seldom used and not readily available. However hiking equipment shops are very common, selling mid-weight equipment such as Deuter, Osprey, Mamont, Mountain Design, etc. One suburb in Auckland, (our biggest city) has 5 Hiking specialist stores within 100 metres. Even my local centre 20 Km from the city centre has two, Tourist centres such as Queenstown, Wanaka, etc are well served.
Prices are slightly higher than in the States, but not greatly so. See https://www.bivouac.co.nz/‎ for a typical range. Take off 15% to convert to US dollars. (You can also get cheap chinese made packs for 60$US, or a dome tent for $50 US).
It is possible to hire equipment as well. Or an economic alternative if staying longeris to buy second hand. Google "TradeMe" for our equivalent to Ebay, but rather more reputable.
Beware of tramping alone. We lose permanently two or three overseas solo hikers each year. The latest was on the Te Araroa trail, which is low level, extremely spectacular, and relatively safe. (Zpacks Joe and his wife recently did it, using his own UL gear).
I'm happy to answer questions.