Workout routine

I'm using some of my own interval workouts along with some on the public workout section. However, I feel they are sporadic and not targeted. I would like to target my ability to sustain power with a group or on my own. Any suggestions on what workouts to use, times per week, length, etc.. I only have about time for 30 to 49 minutes sessions 2-3 times per week. Some guidance would be greatly appreciated.
Jerry