How much money is needed for cambodia vacation?

1000 USD is more than enough. Check the internet for hotel rates and book from there. That way you are able to plan ahead on how much your stay will be costing you. Restaurant meals are quite affordable, USD3-4 a meal. Visiting Angkor Wat is quite costly but definitely a must. Apart from that, there isn't anything else to buy. If you are thinking of buying something, bargain like hell.. Even when purchasing water from the street kids - please always bargain.