Here are a few questions

Can i buy it online or do i go to a store?

Is it worth buying?

What is the difference between a non subscriber and subscriber?

how much does the game cost?

1 - I'm pretty sure you gotta go to the store and buy it, there's no way to download it online (like WoW), besides, I never heard of anyone selling online cd-keys (like D2)
2 - It's worth every buck IMO, even if you subscribe!
3 - Can't answer that, it's nothing major tho. I can't answer it cause I don't know everything myself

Hope this helped a bit!

But wait you buy the game and can play, but if you pay more you get more benefits?

Yeah. And on the Official site there are people who pay who are actually complaining about non-subscribers getting new content...quite a few of them I think.
I'm a subscriber by option, I like the game very much, and paying 10 USD a month isn't THAT heavy on me, even tho I'm Brazilian
But you can enjoy the game very much even not being a subscriber!

So its 10$ usd a month?

Ill probably subscribe

do you know how much american money or canadian money that the game is worth

I heard 30 or 40 USD!
I paid 99 reais on mine (Brazilian coin )