When you are purchasing your first kite you want to buy one that you are going to get maximum use out of. It has to be compatible with you and your skill level.
Be aware that different kites of equal size can handle and lift very differently. It is far easier to learn with a smoother, predictable, steadier flying kite than a high performance kite.
Remember that some days the equipment you own just will not be suitable, the wind may be too strong to fly safely - any kite flown in too stronger wind can be dangerous. Some days the wind will be frustratingly light to achieve what you have set out to do. Limits either way may also be determined by pilot skill level.
For people with competent kite flying experience or looking to get involved in kiteboarding, consider a 4-line or a 5-line kite between 9 and 12m in size to use more often than not.