Have you tried keypresses? Choosing them will give you a much bigger selection of seeds to choose from.
Keypresses is where you hold certain buttons down right as the game starts up. You hold onto them until the Gamefreak Logo shows up. Depending on how many buttons you are willing to go up to, choose one, two, or three. In addition, some people have broken L and/or R buttons so they cannot do any seeds that require them. If you're one of those people, check the "Skip L/R buttons" box. Hope this helps.