For a beginner, have the right equipment is much greater than for a surfista advanced non disaffection from the beginning of this sport and not to spend more time than necessary to learn rigging and sailing.
Important: The best thing is to find an occasion where you set the table to be sold all the rest because in this way are good business. Do not underestimate the cost of accessories such as the apparently minor extension of a tree with its feet.
Dimensions
The best size to start is 5.0 ÷ 5.7 sqm. Only when you know you will affect planar dimensions greater. Moreover, when one day your first purchase 6.5, the "old" you will need 5.5 however when the wind is stronger. It 'totally wrong to start with large sizes as you need to recover from the sailing many times without ill get back.
Features
You will need to orient yourself on a sail-type wave or wave-slalom with 4 max 5 battens, absolutely without camber (now rare); material: not too much surface monofilm pure (one transparent) because it is fragile. Fluent is the monofilm reinforced (double-layer reinforced with plot) this usually to wave sails. The material for the freestyle is very good: light and fairly robust. If you are not an expert in the field: a wave-slalom is a sail with the base rather short and sticks quite divergent among themselves (in a slalom are almost parallel).
A sail with the features mentioned above, is eternal and also the multi for a future wind "bad."
Avoid camber: make sailing difficult it is to arm both for use in water;
Avoid ASSOLUTAMENTE type stuff hyper carbon battens, thin monofilm: we need a sail lasting, economic and above all easy