How to start i3 on server (startx doesn't work)

Startx terminates “no usable desktops”
os-utils-gui and desktop install other des and software which I don’t want
Where do I go from here?

The simplest way is to install the lightdm bundle and use that as login manager. It knows about i3 sessions and can start that properly for you. Alternatively, you can write your own xinit script (but that’s more complex than just making a simple file).