Hi Puating

The answer will depend on your roof structure among other things. I personally prefer gable vents as they can be decorative and they *can* eliminate vent roof penetrations if the roof is small. Ridge vents are great and can also be a detail of sorts, but they need a clear air path from the eaves to the ridge in order to work, and the framing has to be configured for them.

As for "ideal" insulation - I'm a fan of Icynene or other open or closed cell spray insulation, but its more expensive than batt or blown. Could you post a framing plan and some elevations? Do you have vaulted ceilings or flat ceilings? More information would be very helpful

Steve