I recommend you play X, plus its a fun game. There's too many references to X and it won't make sense to why she's looking for Tidus. It's like reading a book but you start in the middle. Kinda Pointless. IT will still make sense but you won;t get a huge sense of Gratification when you get the best ending out of the three. Or you won't be miserable when you get the sucky end xD

You can get FFX for like 30 bucks now and FFX-2 is 50 in the US *70 in Canada* I think its worth it but play FFX-2 if you want without FFX but you'll miss out on a lot.