Since it is winter, and many areas of the United States are starting to experience undesirable golfing weather, what better time to get your shit together and get in shape in the off-season. Golfing doesn't require strength and flexibility, but it sure does help if you can work on both.
Core and arm strength play a big part in your swing. Focus on ab/obliques and superset or circuit it with lower back and glute exercises. Arm exercises such as bicep curls, tricep extensions, forearm curls, forearm extensions will build considerable arm strength and bring speed to your swing. Book end these workouts with a before and after stretch on these muscle groups. Staying consistent with this this over time (through winter) will produce results with distance and focus in your golf game.