Here's some standard figures...
For a Jazz, it's about 9,000 turns for a 60s model, and 8,000 for a 70s model. P bass is 10,000 turns per coil. Musicman Stingray is about 4550 turns. Those all use 42 gauge wire. Ricks use 44 gauge wire, and have changed over the years. The vintage pickups used about 5500 turns, and the newer ones are more around 7500 turns or more.
You can find more of this kind of info over at the pickup makers forum: http://music-electronics-forum.com/f11/
The tone of a pickup is combination of things. The shape and size of the bobbin (tall vs wide), the type and strength of the magnets, what kind of steel you use if you have steel poles, and the thickness of the magnet wire and its insulation, etc.
And with the number of turns, you have the factor of how many turns per layer.
Be prepared to break a lot of wire in the beginning, and trying out new pickup ideas involves winding, testing, rewinding, testing, etc.
But when you get something that sounds good to you, it's a rewarding feeling, and is kind of fun.