Witcher 2's controls are a bit janky, but it's a solid game in and of itself for the story alone; if you can stomach some pretty bad mechanics to enjoy an otherwise decent product, I'd say start at #2.
Witcher 1 is... so bad it's kinda comical. I'd just pull up a story summary of Witcher 1 on youtube and call it a day. If you're a masochist, go ahead and give the actual game a whirl; but I'd recommend modding the snot out of it to at least make your character OP as fuck, allowing you to mostly skip the god-awful combat. But even then, the only selling point is the story, which again you can just pull up on YouTube.
That said, you can dive into 3 with zero knowledge of the previous two and be just fine. There are things that will go over your head, but nothing significant.