X/Y will be my first Pokemon game since original Red. Would someone be so kind to explain me how Poke-Transfer works? I am not a "genwunner" or anything like that, but would love to have some old Pokes available in Gen 6 if they are not by default available there. Would I have to buy ALL previous generations games along with GBA and DS and transfer the Pokes in manner; 1->2->3->4->5->6? How will that work? Or is the game which has Pokemon I want enough and no need to buy them all in order to transfer them generation by generation (skip directly from I, or III, or IV to VI.)?

Thank you