Strength is very important, should be the first skill you train to 20+, don't put points into it, just train it.
It won't help that much breaking tackles since you should be running on elusive, but it will help a little with that. Where it will REALLY help is in holding on to the ball. It helps at least as much as carrying if not more.
It will also help when you are actually playing CB, you will tackle better and cause more fumbles.
After you train strength to 20+, then train carrying to 20+, then confidence.