Maybe I have not expressed myself clearly. I do not want to skip the categories. I just want to hide the categories for my users. Is that not possible?
It's possible, but it's not easy. Some error message redirects will send to the category. There are links that'll return the user back to the category. The links can be removed by editing the template files, but the redirects are built into the core. I recommend re-organizing to make more use of Categories as it'll be much easier to setup.
We'll be having internal discussions about GJs future after CB 2.0 stable, but my general idea is to go a mot "tags" based approach and getting rid of categories. The tags could then act as pseudo categories. That's just an idea though and we'll be discussing all of this and more after CB 2.0.