You can enjoy the 3 games separated, but the experience wouldn't be complete. You'll get insight as to why (I'm gonna avoid spoilers) white bearded guy think and acts the way he does. And believe me, after playing The Witcher 1&2, you're gonna be as (SPOILER) as him.
Now, do your homework and run to buy and play them cause CDProjektRED deserves every bit of money, it's one of the last AAA artisan developers, so much mastercraft into every bit of their games.
I've got close to 500 hours between TW1 and TW2.