And I've been dabbling in Donna/Master fics so what does that say about me? I just love how characters interact

I definitely agree with you about being interested in how characters interact. Donna, especially, I find fun to read when she's paired with other people because she's well-rounded and strong enough a character to push a story along. I like reading the different dynamics. At the moment I'm curious to see how she would play off the Master (especially after the missed opportunity in EoT) so I'd really be interested in any Donna-Master fics you've written, are writing or have read.