Welcome to IIS Joe
My little bit is that you should easily see Saturn's rings with the 8mm eyepiece. 90x is more than enough to see the rings. You should be able to see the cloud bands on Jupiter as well
Don't forget the moon.
A couple of bits that may help:
- Your scope is basically a 3" and at the rule of thumb of 50x per inch that means that 150x is your maximum magnification on an exceptional night. Most often the 8mm lense will max you out as this is controlled by the seeing not the scope.
- More magnification does not mean better views, that is a marketing gimic to sell cheap telescopes. Magnification is mostly controlled by the seeing, if the stars are twinkling then the seeing is bad and you will not be able to use any great magnification.
- Only use good barlows otherwise they just magnify the problems and do not help at all. A bad one will actually degrade your image.
A couple of questions, what type and brand of scope do you have? Does it take 1.25" eyepieces? What ype of mount does it have?
If you can answer these questions or post a picture then we can be of much greater help.
Cheers