In typical seeing condition you should be able to use a magnification (see here) of about 25-30x per inch of apperture, so for your telescope that is about 100x, in exceptional condition you could push that up to maybe double that. Also the more magnification you use the less contrast you will have in the image, so really you want the lowest magnification that gives an image size compatible with being able to see the bands since you will be contrast limited.
You will find simulated images of Jupiter through a small telescope here and Saturn here. Though personal experience suggests that the simulated image of Jupiter through a 3" aperture is optimistic. IIRC a suggestion of banding is just about at the limit of what I can see on Jupiter in the small scope.
One of the things I find that can degrade my ability to see detail at the telescope is stability of the mount. So when viewing with a lightweight (aka flimsy) mount wait for low wind conditions and don't touch the telescope or mount. The quality of the optics also makes a big difference. What kind of eyepiece are you using?
I am guessing that your telescope is this