There are no "Sage" or "Jill" paths, at the moment (till the end of episode 8). There are different gameplays depending on your affinity (dik, chick, neutral), in fact.
Anyway, I can tell you that your gameplay experience is going to be different whether you date 1 main girl only or more than one.
Some choices will have a major impact in the story, some won't.
Josy or Maya as the main girls? it's up to you, in the end (it depends on what you answer Derek, after all). My honest feeling is that Maya and Jill are far more important than Sage, Josy and Bella.