Let see what I can tell you about Spike and Dru.
Well iI knoe that they kicked @$$ together!!!!!
I don't reall know much about them so bare with me.

I knoe that their sire is Angelus.
Angelus made Dru insane and then turned her.
I'm not sure what he did to Spike, but i know that he turned the poet Will a vamp.
In Season 2 Dru and Spike came to Sunnydale to raise some havoc.
Angel then lost his soul became Angelus again nad joined their side.
He then was getting on Spike's nerves.
Spike and Dru ended up leaving.
But in Season 3 he came back wanting to do a spell for Dru who had left him. he then left again. but then came back and stayed in Sunnydale