Which adaptor you buy depends on the mount of the lens you buy. So for example, if you get a nikon lens, then you'll need a Nikon F mount to micro 4/3 adaptor or if you get a minolta lens, you need a minolta MD mount to micro 4/3 adaptor etc., etc.
I feel like lenses are kind of a subjective thing. They arguably have the largest influence on you final image. So what lens you need will be dictated by what kind of look you are going for. At least that's what I think anyway. :-)
I would definitely recommend getting the kit lens with the camera. I got a GH1 body only because I already had a bunch of old lenses but now I'm really wishing I had a nice simple zooming autofocus lens with image stabilization so that I would just quickly pop off a shot now and then or shoot hand held any time I felt like it. As it is, I always need to use some kind of rig and I often miss a shot because I'm busy focusing. Not that I would use it all the time it's just nice to have for those quick, in the moment times. From what I hear, the panasonic 14-42mm is actually a really nice lens. In fact, I would recommend starting with that, shooting with it for a while and seeing what it is that you feel it's lacking and then using that to inform your next lens purchase.
Have you considered the GH2? Bang for a buck especially with the GH3 around the corner. You also get a lot of very nice old prime lenses on ebay for little money.
