This could be stating the obvious but just in case:

IDL is a good way to go if you have P8, vary the ambient value on each of the flame materials.
If its an animated scene use a noise node fed into the ambient value to vary the flame per frame.

Otherwise, you will need a point light per candle and set the fall off to a short distance. Again, if animated, a noise node fed into the light intensity value will make the candle light flicker.

Make sure your flame object is set to not cast a shadow. 

Ray Traced point lights or IDL they will both be  long renders but I bet it will look great!