If you're willing to pay $5, you can use Pokémon Bank to mass-transfer boxes of Pokémon. This is the most efficient way for transferring entire PokéDexes. However, if you only want to transfer a select few, just trade them from OR to Y for free.
Please take note of the following:
1 - You will need two 3DS systems to trade them over, while PokéBank only requires one.
2 - Make sure the Pokémon you're trading from ORAS don't know any ORAS tutor/level moves that aren't available in XY, and aren't holding any ORAS exclusive items (namely Mega Stones).