IMO setup is more important than anything, so that'll be my advice, since I'm not sure just how much you know. As far as specific gear, I'll leave that up to everyone else.
are a matter of preference and jsut something you need to try a lot of. I'll stress that they are the most important part of your setup
. When your heel is in the back of the boot, your toe should be touching the front (unlike how sneakers and shoes are normally worn). Your toe shouldn't be scrunched, but definitely touching. They should be comfortable and preferably have a heat molded liner. I'd recommend orthotic inserts to everyone, especially if you have foot problems. The insoles that come with boots are all garbage
length is preference but as a rule of thumb you should first go by your weight. In general, the heavier you are, the longer your board should be. If you're a shorter rider with short legs and heavier set, then you need to worry a bit about stance width (longer boards have a wider base stance width), but usually it's not the case. Decent sizing guide here Sizing Guide | Snowboards Shred-O-Pedia
, however you might want to go a couple cm shorter than that suggests for your weight, since a shorter board is easier to maneuver. Leo is right about the 158cm range. I cut my teeth on a 157, which is way longer than I should have ever ridden for my weight, and it made it harder to learn than normal.
3) Not sure if you have your warm gear
planned out, but you should dress in 3 layers. I dress in Under Armor cold gear 3.0 for my first layer, microfleece pants and sweatshirt for my second layer, and a waterproof shell jacket and pants for my third layer. If it's really cold I have a special wetsuit like coat that I can wear instead of my sweatshirt, but i get cold easily. I personally make sure I get really good gear so I'm as warm and dry as possible. I'm pretty sure it gets cold as hell in NZ, so make sure your third layer is waterproof/windproof. Good goggles and gloves make a difference. Make sure you get goggles with lenses that are polarized to match NZ's conditions (low light, medium, bright and sunny, etc.).
setup is important. We can recommend all the brands in the world, but if you don't know how to set them up, they're all useless. A couple tips, your bindings should be centered perfectly in between the heel and toe side of your board, and your boots should be centered perfectly on top of your bindings. As far as stance width I don't know your height, but 22-23 cm is probably acceptable. I'm only 5'6" and my stance widths range from 20.75-22 cm on my boards. As far as angle of your bindings goes, 13 degrees to 18 degrees outward on each binding is probably good for you, since you want to ride switch. Just go with what feels good.
5) As far as progression
goes, start as small
as you can, try to achieve the little goals first, and you'll feel great and have a lot of fun. Start out too big with anything and you may get hurt, become intimidated, and then learn at a slower rate. It also helps to hang with some riders that are above your skill level because they can teach you a lot. If you're having fun and not getting hurt, then you're doing it right.