Unless you really specialize in spriting pokemon, there are a few tips for a better chance of becoming staff:
Be helpful, do things that makes Pokemon Reborn a better place.
Try get a good reputation around players, get a good forum rating (without asking for these) to show that you are good.
Show that you are active, especially in the forums.
Never break the rules, show hatred towards another player or flame/fight back.
Asking a few times might be all right, but constantly begging to become staff will greatly reduce your chances of becoming one.
If you are recommended by multiple staff and meet all of the following requirements above, you have a good chance of becoming staff.
I am looking for professional GFX/spriters, photoshop is recommended.