I learned to sail through a community boating program.
We could sail all summer for $200. Best $200 I ever spent. It was all run by volunteers. You meet great people, with bbq's etc. You learn to sail, even race. Great way to pick up a date....
I would check to see if there is a program like that near where you live. Then, after you learn how to sail, you'll see which kind of boat you like. Our program has 9-10 different kinds of boats, all sizes and shapes. I bought two different boats after that. One small dingy (Cape Cod Mercury) and the other is a day sailor called the Cape Cod Sheilds. The Shields is mostly used for racing.
Learning to sail on a lake is great, because the wind will shift on you constantly. Teaches you to be alert!