Low light, no flash, indoor photography is a 'battle' with the exposure triangle. At least that's how I think of it.
Assuming you are photographing people, reasonably still (standing, talking), 1/60th shutter speed will work for many of the shots, but there will be times that you'll end up with someones' hand blurred, especially if they 'talk with their hands'. Semi-posed for a group shot, 1/60th should work, but there will always be somebody with eyes closed, or not smiling, or in some kind of less-than-desirable pose. Some people are touchy about their nose and photographs that make that too prominent are a no-no. In short, whenever I take group shots, I take at least 5, more like 10, in rapid succession (as fast as I can press the shutter button), and then pick the one that came out the best. Of course, having a longer focal length (zoomed out), you may need to go with faster shutter speeds to stop camera shake and/or people that move too fast. Unfortunately, looking at the images on the LCD after they're taken won't reveal any subject motion or camera shake unless significant. If you can go to the venue ahead of time and take some test shots, it would be advantageous to see how slow you can go.
It's all about light. And having a wide aperture, if not maximum, then close to it, is required. I don't know how a Lumix camera behaves, but at large apertures, say f2.8 and larger, the depth of field gets pretty thin, and can result in some people in a group shot being in focus and others not. Let's say you decide you need f4.5 for a 'reasonable' DOF at 15 feet. Maybe the Lumix does better in the DOF department, I don't know.
But once the two 'critical' factors are decided, then it's time to set the ISO to get a decent exposure. Let the meter in the camera be your guide...at least as a starting point. Then take a shot or two. Look at the results. Over exposed? Under exposed? Adjust the ISO to compensate....up to whatever limit you've pre-determined the noise level is no longer acceptable.
Lets say ISO 1600 is about as high as you want to go (I have no idea what the practical limits are for your camera). You may find that even at ISO 1600, the meter is showing under exposed and/or the results on the LCD are clearly too dark. Here's where the 'battle' comes in. Now then, you have a choice of how to get 'more light' to the sensor...wider aperture (thinner DOF), slower shutter (maybe some blurring), or higher ISO (more noise). Pick one. Pick two. Maybe a little bit of all 3. I've tried them all. Most often, I'm happy with slowing down the shutter speed and getting maybe a blurred hand movement in an otherwise all sharp picture. But when you're at 1/60th and slower, the non-blurred pictures get hard to come by. At 1/20, maybe 1 in 15 are OK. Yes, 1 in 15! at 1/10th, maybe 1/20-25...and that's with the camera on a monopod and me leaning against a pillar! The slower you shoot, the more shots you'll need to take, just to get a keeper!
I've found that experience is the best teacher in low light. I've tossed hundreds, if not thousands of low light shots because of over/under exposure, subject blurred, camera moved, too high an ISO, you name it. Hey, at least it's not the 'good old film days with ASA 64 (ISO) considered 'high speed'. The solution is get used to it and take lots of pictures to choose from, or upgrade equipment until you get what you want. Better have lots of money for upgrading.
