I can read in the documentation:
Sulu Instance At first you create a Sulu Instance. It could be seen as a single installation or one pool of data. Its real live mapping could be a company or an organization.
and when I make a user with the console I can see that there is a "system", the name is Sulu, how can I make more of them. I'd like to have one per customer, in the way to have a separation of data for the users of different companys.
The system you are reading about in the create user command is not about separating data, it allows you to build an own set of permissions for another application used along with Sulu. This way you can e.g. build a custom intranet for a customer, and have a separate set of permissions for Sulu itself and the intranet. You can read more about this here: http://docs.sulu.io/en/latest/cookbook/securing-your-application.html
If I understand you correctly you would like to have separate Webspaces. Each webspace has his own URL, and contains its own content tree. So just create a second webspace xml file as described in http://docs.sulu.io/en/latest/book/getting-started/setup.html#webspaces, and you'll see another item in the side navigation.
You can set permissions on these webspaces using the user roles. If you edit or create a new user role, you'll find a new row for your webspace, and you are able to adjust the permissions accorddingly.
