This is the kind of thing that you are better off buying then building. The ability to design things only comes after a period of taking things apart, building some things that other people have designed and then branching out on your own.
You might wan't to start with a simpler circuit which will be useful later. It is called a multivibrator. It oscillates back and forth between two stable states with a predictable frequency. I suggest that you try for any frequency between 500 Hz. and 5 KHz.
If you can find a circuit, acquire the parts, fabricate, and debug the circuit you will be well on your way.