To be honest, you can feed them as much as they are willing to eat. A good way though to start out would be to drop in a cricket or other insect and see if he eats it. If he does, drop in a couple more. Anything that is uneaten you can take back out of his enclosure. You'll probably find that feeding him every second day should be sufficient.

For information on what to feed him as well as general information, try going here.