You can organize your groups into different topics in the *Group* buffer. First make sure gnus-topic-mode is added to the gnus-group-mode-hook, then use the options in the Topics menu to organize your groups into topics.

You can use gnus-topic-goto-previous-topic and gnus-topic-goto-next-topic (bound to T M-p and T M-n by default) to jump to the next/previous topic but I find these command awkward as they do not move up/down levels of indentation. I prefer to use the following commands instead:

    (defun gnus-topic-goto-previous-topic-line nil
      "Goto the previous visible topic line.
    A replacement for `gnus-topic-goto-previous-topic'."
      (goto-char (previous-single-property-change
                  (line-beginning-position) 'gnus-topic nil (point-min))))
    (defun gnus-topic-goto-next-topic-line nil
      "Goto the next visible topic line.
    A replacement for `gnus-topic-goto-next-topic'."
      (goto-char (next-single-property-change
                  (line-end-position) 'gnus-topic nil (point-max))))

Another annoyance for me is that by default the <tab> key is bound to gnus-topic-indent, and I often found myself pressing it by mistake when I meant to fold a topic. By default topics can only be folded when the cursor is on a topic line. The following command fixes that:

    (defun gnus-topic-fold-this-topic nil
      "Toggle folding of current topic."
      (gnus-topic-goto-topic (gnus-current-topic))

I bind this command to <tab> to avoid the previously mentioned annoyance.