Since you do not have Pokémon Bank you will need 2 3DS systems, 2 2DS systems or 1 3DS and 1 2DS basically any combination of the 2 and then you will be able to trade between Y and Alpha Sapphire but buying a 2DS or 3DS is more expensive than buying a yearly Pokémon Bank subscription which is just about $4.99 but that doesn't count tax provided your state is one of those states that charges tax.
You will have to trade with another 3DS.
So your 3DS is North American? If so you could buy a Nintendo E-shop gift card.
well u can get the free 30day trial of pokemon bank free no matter where u live
GTS..have to be fast