I'm by no means an expert on ringmod, but here's a few observations:
For me, it does take some(considerable) experimentation to get really
good sounds from Ion's ring mod. Although the ringmod signal is
generated by osc's 1 and 2, their levels in prefilter mix should be
zeroed for maximum effect; have only the ringmod level turned up.
Pitch of osc's 1+2 is the key for good ringmod effect; they usually
need to be octave shifted relative to each other. Also helps to assign
a mod wheel to alter pitch of one of the osc's; this makes it easier
to fine tune the ringmod sound. Ring mod will generate more complex
harmonics when you choose two different osc waves for osc's 1+2
(pulse+saw, square+tri, sine+pulse, etc). If osc 1 or 2 is a pulse
wave, a little pulse width mod provided by an LFO can add interest.
Using an LFO to alter pitch of one or both osc's really helps add
complexity to the sound.
OSC 3 has no effect on ring modulator