Stefan,
you can take good images with a flea3. I did for many years and these are just a few of them.
Saturn in 2012
Saturn in 2013
Mars in 2012
Primarily you will need good seeing. Good seeing provides quite still conditions like those
seen in this video. If the seeing is not good it will be blurry.
If you are using a barlow then your image scale/focus will change and the gain/exposure settings will be too fast so you would not be able to see Saturn. You would need to up the gain/slow the exposure rate and look for Saturn which might well be out of focus a lot. Once you have the out of focus Saturn visible then you can focus and star working on exposure and gain.
I hope that helps.