Good advice here, especially if your main interest is ultra close-up type of macro work. The thought struck me though that there are some other avenues that you might (or might not) be interested in exploring.
The world of the very small is fascinating, for example seeing the normally invisible details of a fly's eye, or a spider's many eyes and strange mouthparts. Generally speaking however the greater the magnification, the more difficult things can be to get right - dealing with the very thin DOF, getting the centre of DOF placed just where you need it to be, the effects of camera shake, the effects of subject movement, the difficulty of getting enough light onto the scene and, when using flash, delivering the light in such a way to avoid hot spots (e.g. diffusing the flash, which is a bit of an art form in its own right).
It is easier to deal with less magnification, for example taking pictures of whole insects, spiders, snails etc, and personally I find there is plenty to explore at that scale and plenty of opportunities to make pictures which are by turns fascinating, odd, beautiful, instructive etc. You may also find you have more latitude to use smaller apertures, higher ISOs and slower shutter speeds. I have been using a bridge camera until recently, but I have recently started using a Panasonic G3, which is closer to what you are using. With the G3 I am routinely using f/22 for most macros, I often use ISO 800 or ISO 1600, and often use slow shutter speeds. For example,
this image used ISO 800, f/22 and 1/20 second (it is not an isolated example btw).
Even if you want to concentrate on higher magnifications, you may find working with lower magnifications gives you a good entry point and platform to work up (down?) from. And who knows, perhaps you might find some of the lower magnification stuff interesting/involving in its own right.
