The easiest way I have seen to make you r own car rims is to buy "spun" sections of rim, and bolt a machined plate to them. They are called 3 piece wheels. You can buy replacement spun sectioins with different backspacing, so they will match your car.
Do a google search and you will find companies like this: http://www.simmonswheel.com.au/faqs.html
See how the wheel is 3 parts? You can make the "plate" part, and buy replacement rims. Plus, if you bend the rim, you can replace one part, not the whole rim.