Whats the most effective martial art with the best overall health benefit,and how often should you practice it?

As the other answer clearly states, there is no "most effective martial art". As for how often to train, do it more than once a week. Do not treat a legit martial art as "just an exercise, because I guarantee you, they are more than an exercise. Just train how you want, as long as it is serious. As for your question "is most martial art training obsolete because of the civil world?" Ha, no. Definitely not. Studies show that over 15,000 people are attacked everyday in broad day light. If anything, it's easier for people to kill others now. Even if the world were peaceful, learning a martial art is still a benefit.