Well, you must follow these guidelines to get the Shaymin. Are you ready?
1: It starts at a really low level, like 5 at the highest.
2: It is the only pokemon that you start with.
3: There MUST be a good backstory behind it. (This is probably the most important one.)
4: No Gracidea flower for a very long time. Like, until after you get six gym badges.
5: When you have those badges, you must complete some long and drawn out side story to even find Gracidea Flowers for Shaymin.
That's what we came up with. Can you deal with it? And I'm glad to see you're back.