Save yourself the pain... I'm serious.
Capturing the pokemon is the most annoying thing ever. And the worst thing is the reward. You DON'T get to keep them! The animation is kinda cute, sure, and I like how they follow you, but it's just not worth it. I play games for fun, and that's what this game completely lacks.
If you complete the game, you are able to do a excruciatingly hard quest and at the end you get a manaphy egg that you can trade into D/P and will hatch. You can also breed it to get phione, but I don't see myself completing ranger anytime soon. If you do, congratulations!
I feel like my touch screen has gathered so many scratches from this game, circles are permanently there. And that's why you should probably get a screen protector if you value your ds's condition. :)