which anime do you think i should buy?

Well, on Amazon, Skip Beat is about $50 while Ouran is on sale for $35, and The blu-ray version is on sale for $25. However, it depends on which one you want the most, so we can't choose that for you. I would recommend buying your favorite if you have the money. Otherwise buy the cheaper one for now and save up for the other. I'm assuming you've seen them both. If you haven't though then just look at the genres and summary of both shows and try to figure out witch show is more suited to your taste.