For awhile I considered Brian because it started with the same three letters as my birth name, but in the end I went with Devin Scott because that's what my parents would have named me had I been MAAB. It also worked out well that Devin is a pretty gender-neutral name, since I still present female in most situations (which I wasn't planning on when I changed it).
I'm still getting used to getting called Devin. It's been my legal name since the end of May, but sometimes it still doesn't feel like "me". There's a certain disconnect, like even though I know people are referring to me, they don't actually mean me. It helped a few times over the summer when I was getting yelled at by my boss and it almost felt like he wasn't really saying those things about me, but usually it's just disconcerting. Sometimes it feels like I don't exist-- like this Devin person everyone is referring to is a figment of my imagination. It's getting better, but it's taking a lot longer than I thought it would. And the fact that my immediate family still calls me by my birth name doesn't help, although now when I think of my birth name, it REALLY REALLY doesn't feel like me.
At least I'm finally starting to look when I hear it and I'm getting a lot better at remembering to introduce myself as Devin. I had an interesting episode during my interview for my current winter job where I did everything right: walked in, nice firm handshake, made eye contact, smiled, and said confidently, "Hi, I'm *birth name*" and her face just fell and she looked so confused because that wasn't the name on all my papers and I wound up having to explain how I changed my name. Not how you want to start to an interview, but I got the job, so it couldn't have been that disastrous.
So yeah-- it takes awhile.