Day Trips Magao Caves

1. Does anyone have information on which are the best caves to visit from Dunhuang if we only have 1 1/2 days to visit.
magao -
Longmens
Yuangang caves

2. Information and costs of a Private Car Rental to take us to the caves... round trip including gas and spending the day at the caves ( at least 4 hours in the caves )... $$ and contact information