Ugh finally done; took me ages.
The quality is really bad though: does anybody know how I can make it better? (dpi is 300)
EDIT: Fixed
I find this to be quite a cute piece and I enjoy the circles around the card, they really help fill in the negative spaces. However I do have some issues with this card. First off, I feel that the diamond around the Oddish looks really rushed and I can see the line overlap on its leg. I also find it rather rushed due to opacity overlaps on the diamond, doesn't look clean or constant. I would keep it a solid color if I were you.
As for the whole piece, it looks like you merely used one layer (I can tell because of the shading overlaps). If you used multiple layers, it will reduce the chance of colors overlapping (you can use one layer for lineart, the coloring below it and so forth).
Finally, I find that the suite diamonds are out of shape. If you can, use the line tool over free hand, it will make your lines much cleaner (I'd recommend using it for the center diamond as well.