(This is assuming you are American, apparently this book sort of assumes you are from there, since it lists American suppliers. It may also use American units and stuff, but there will be loads of other books if its a problem)
Or, you can dive into the deep end and try building some that have already been designed by other people. This is one I've always wanted to try:
They have a wide range of projects ranging from extremely cheap and simple to really quite complex looking ones- all of which seem to have step-by-step instruction as to what parts you need and how to assemble and program the robot.
Explore the website, see if there's anything you want to try!