Depends on your weight. At 70 - 80 kgs. a kite in the 16 to 17m range will be good for 10 to 16 knots. Many people would recommend that you learn with a smaller kite - around 12m, however, it is certainly possible to learn with a larger kite.
You should at least spend some time flying a small trainer kite, before going out with your traction kite - your kite (& your ass) will thank you for it.
Probably not a good idea to get a really high aspect kite at first, but, again, it could be done.
As for the board, you would do yourself a favour if you got hold of a large board, either a directional or a twintip, to learn on. Used big boards can be bought very cheap. They will make learning much easier initially.
IMHO the most important factor in learning is not the equipment but the CONDITIONS where you are learning. You will not feel comfortable in strong winds at first: if you have some where you can run downwind it will give you a lot more time on board to develop your feel for planing with the kite. Shallow water will also help a lot as it will make crashes less traumatic & time consuming. In ideal conditions it is possible to get the hang of kiteboarding quite quickly.
In difficult conditions you will spend a lot of time swimming.
Finally, forget the idea of "windsurfing-when-it's-over-16-knots". Soon you'll be getting a complete quiver of kites