That's not an easy question because every concert is different, every moment has different lighting (sometimes super bright, sometimes spotlight, sometimes dark, sometimes still, sometimes moving fast...) In general concerts tend to be on the darker side, so try to use brighter exposures. This, however, conflicts with trying to get crisp pictures of fast-moving subjects (to achieve that you have to speed up the aperture time, which takes in less light).
In my experience, unless you want to print the pictures, taking video and letting the phone adjust the settings on its own usually produces much better results for quick captures off the video.