About much muscle [mass?] is gained on T?

[R.A.A]

Hey there,

I'm getting ready to start exercising more, going to the gym a few times a week, eating a bit healthier (but not much! xD) and that sort of thing. I was wondering, just out of curiosity how much muscle mass did you gain after being on T for [x amount] of time? Did you have to exercise and diet like crazy to get it, or did it just come naturally, because of the hormones?

I haven't started HRT or anything, I was just thinking about how much definition I wanted in my arms and if I'd have to spend crazy amounts of time getting there.

RAA.