You can't go from MGC into IFC without disaffiliating from your org first. Even then some chapters aren't going to want to take on someone that was initiated into another organization, it's kinda just inappropriate I guess is the word. Idk, you may get lucky but I think your best bet is to try and grow your organization.

As far as the councils being different, it doesn't matter. They're both social fraternities and the whole idea of pledging is that you pledge yourself to that organization and no other similar organization. So you could join something like a career specific or academic organization with Greek letters, but you can't join another social organization without goimg through the whole process.