from my experience... 15-20 knots in a nice steady sea breeze. (Mind you, I'm on the heavier end of the scale

)
This, of course, depends upon how "beginner" you are, how heavy you are, what size board you have, and of course what kite you're flying.
Best thing to do is get lessons, and don't stop the lessons, until you are sure of what is safe and what isn't safe.
Kiting with competent and responsible kiters, that will guide you on the day, is also in your interest... and everyone else's best interest.
rgds,
AzzA