Firstly congratulations on taking delivery of your B30, I hope you enjoy her as much as we did ours.
With our B30 we used to roll away some genoa early before considering a reef in the mainsail. We always found that she would round up really quickly in gusts leading in the early days to one memorable heart stopping moment close to Calshot Spit buoy, rolling away some genoa early helped with keeping balance on the helm.
As for when to put in a reef, our first reef normally went in somewhere round 15 knots depending on direction and seastate. One of our crew can suffer badly from seasickness so we tend to reef based on comfort and ensuring that sailing remains enjoyable for all the members of the crew.
Hope this helps,
Paul.