Without knowing what frequency you want it to work on, it's not possible to give a schematic
but before you actually decide what frequency, you have to find out if you need a licence in your country
some countries insist on licences no matter how low a power your going to transmit.
I do have one schematic for you that I can guarantee works, although it isn't a walkie talkie, it's more a telephone but it will work better than anything you can make for the same price
What You Need
An adult to help
Two metal cans, clean and dry (or plastic/polystyrene cups) Be sure that there are no sharp edges on the cans to cut yoursellf with
Ten to Twelve feet of a piece of small diameter string such as kite string or nylon string
What You Do
Make a 'Tin Can Telephone' by punching a small hole in the bottom of each can.
Each hole should be just large enough so that the string will go through.
From the outside, insert one end of the string into the hole in one can. Tie a couple of knots in the end of the string so that it will not slip back through when pulled tight.
Do the same with the other end of the string using the other can.
With one person holding each can, move away from each other, stretching the string so that it is tight.
One person talking into one can sends vibrations through the tightened string to the other can.
The person with their ear to the other can will be able to hear what was said.
Old idea but still works well.
Sometimes the simplest of things work better than complicated things.
Karen