I don't know what my balance between strength, cardio, and flexibility exercises should be. How many times a week should I be doing each?
It all depends on your goals anon.
A good balance would be 2-3 strength trainings, 2-3 cardio sessions and stretch after every workout. Add some yoga if you really want to be flexible.
We only have so many days in a week so spend more time doing what will bring you closer do your goals.