I agree with all of the above,
I find that I can have really good sail on a 12-14 knots day with the right setup, and as the wind is not strong the water is flat.
I use a 8.6 sail, with a 122liter RRD XFIRE slalom board, using 46-50cm fin, few pumps will get you flying.
Look at a 7.9 to 9.0 sails, I personally like 4 cam sails, but they are heavier, so perhaps a no cam or 2 cam sail would be ideal to keep it all light and fun.
Good luck!