I would say "a,b, c, d, and so on."
You are more likely to hear forward instead of onward. I would never say move onward, but I would say move forward. ( this would mean straight ahead and not just further ahead) You could say "go on" meaning continue, but I don't know anyone who would say go onward.
Onward is usually used as an exclamation and often with a strong sense of purpose i.e "Onward! To save the day!"
Hope this helps!