Auto takes away a bit too much control. Try using P(rogram) mode which will instill enough control with the camera but gives you some back to make creative and technical decisions. I know it's tedious, but I strongly urge you to read through the manual and understand the controls - both physical and software (menu) related. Since Comic Con is mostly indoors (although somewhat well-lit), remember to use the pop-up flash to fire a bit of fill light.
In parallel, your settings will also be dictated by your choice in Post-Processing. All photos benefit from some optimization on the computer following capture in the camera. If you are just starting out and don't have a preference, consider managing your photos through View NX2 (which should come with the camera, otherwise available for download via Nikon) until you have a better idea of what you want to do.