Level settings are dependent on which mics you are using. In general I find that I use the Mic in, low (Plug in Power off) with a battery box and my AT853 / battery box.
Your mileage may vary.
I'd also turn the limiter on, if you don't need it it doesn't hurt and if you do need it it helps.
I'd take my rig to a few open taping shows, and notice the correlation between show volume and levels while adjusting the gain knob.