What kite should I buy?

This is a hard question to answer as everybody that you ask will come up with a different answer.
We all like different things in our kites, and every rider will swear that their kite is the best kite there is.
If you are a beginner looking for your first kite, here are a few pointers:

1 - Don't spend all of your money on a brand new top of the range kite.  You are a beginner, you are going to crash your kite many, many times.  You will learn the thud sound that a kite makes when it hits water (or worse land) at high speed.
2 - Check with local boardstores or trade forums (http://www.trademe.co.nz/) for used goods, try to pick up something from last season or the year before that doesn't have too much damage.  A demo kite from a kite school can be a good deal.
3 - Don't buy a kite that is too big for you!  You are a beginner, the last thing you need is to be way overpowered when you don't know how to safely control your kite.  Look at the average wind conditions for where you are going to learn and buy a kite suited for you based on that.  Your kite size will depend on your weight and the wind, I'll post something later on about picking the right kite size for your body.
4 - If you can pick up a 4 line kite for your first kite, do it!  5 line kites have their place, but as a beginner, its one more line for you to get tangled.
5 - Buy a bow kite.  Yes C kites are fast, but a bow kite is easy to control, is much more forgiving and will relaunch easily.
6 - Pick a stable kite.  Kite are designed in different ways,  you have beginner kites and trick kites.  Beginner kites allow you to twitch the bar without the kite responding very quickly.  This is good, as you will be thinking about lots of other things (where is my board, are my hips out, am I going upwind) and sometimes you will pull on the bar without meaning to.  A stable kite will allow you to do this without the kite responding very quickly.  A fast turning kite will respond to everything you do to the bar, this means that it will respond to your every mistake, and you will get quite frustrated as you crash your kite again and again.  The time for fast kites will come, but for now start with the stable kites.
7 - If you are kiting in water, buy an inflatable kite.  If you are kiting on snow or land, buy a foil kite.  Foils don't like to get wet and so are no suitable for water kiting unless you have enough control to know that you will never crash your kite.  Foil kites are easy to self launch and land, making them great for land and snow when you are strapped into your snowboard boots or on your landboard.  Remember that kite sizes are not comparable between foils and inflatables, a 10m foil will give you a lot more power than a 10m inflatable.