If you are serious about macro you will need to get a longer macro lens to start with, either a 100mm or go straight to the sigma 150mm. These will give you more working distance but not stronger macro, they are all max 1:1, but the longer lenses make it easier to add diopters to go beyond life size (diopters give a stronger effect when the primary lens has a longer focal length).
The other tool to boost magnification are teleconverters and they don't reduce the working distance but do reduce the amount of light reaching the sensor, one stop for 1.4x, 2 stops for 2x etc.
Just remember, the farther you push the magnification the more painful the experience becomes. Unless you have a lot of experience already I think you will be better off by just getting a 100mm lens and then consider adding TC or diopters from there on.
Bart