About getting the low dose from your therapist 1st visit, I've never heard of it happening before.. But I've not heard of it NOT happening, either. I guess that's something you'll have to ask.
My experience with therapy wasn't very typical, because my parents, though accepting, don't want me to start T. I missed my appointment in December of 09 where I WOULD have gotten my letter because I fell asleep and slept through it (D'oh!) And then my therapist had surgery so I couldn't go see her again until February 2010. When Feb came around my parents made it clear that I wasn't going to be allowed to start, even though I told them around October that I was going to (They didn't take me seriously)
So I had to wait until 6 months before transferring to VCU from my current college, which would have had me starting in March of 2011, because that's 6 months between August 2011 when I would have been transferring. They wanted to give me the time to make some changes needed (like voice, hair, muscles) so I could pass at VCU. They didn't want me to start at my current college because... I don't know really, their reasoning was for the people I already knew, but they all either knew me as male or as a transguy. And on top of all of that, I realized that I would have to stay in my college I'm in now for an extra year for complicated reasons, so I would have originally had to wait an EXTRA YEAR, ala, March 2012. (I convinced them to let me start in March 2011 anyways.)
So I waited because I love my parents and I want their approval for everything because I don't want to break any trust.
But starting this semester left me with having to re-introduce myself as male to everyone. There were so many new students that all thought I was female, it was too much to handle all at once. I went from EVERYONE knowing I was male, to only the handful of friends that had similar break periods as me. That along with having 4 hard huge project oriented classes which stressed the hell out of me, I dropped out of 3 of them, leaving only Glassblowing because when I'm in that class, all I'm thinking about is the molten glass at the end of the rod and the 2,400 degree furnace 2 feet away from me XD;;;
When I dropped out of the classes, I also told my parents that I WOULD start T. I made the decision to do whatever I needed to do to be happy and if they didn't like it, I would leave. It became apparent that I needed to do things for me, not for them. They accepted grudgingly, and I got my letter and made my appointment (which is next thursday yaaaaay)
So yeah. My wait period was a little less than a year because I wanted to be complying with my parents wishes.
My experience with therapy was not just about GID. I have severe anxiety and depression, and a lot of history with dropping out of school due to panic attacks and the like, so we talked about that alot. We talked about what kind of a role my GID played in my life, and once I was confirmed to be trans, it kinda got pushed to the background. We talked about my actual issues. Of course we discuss the GID every visit, but since everything got smoothed out, it's mostly just regular old therapy.
So basically your therapy experience will depend on your mental health. If you are a happy and functioning person, your therapist won't really need to talk to you about anything other than your transition.
I can't remember if real life experience is required for starting T. It's been a while since I read the Harry Benjamin thing, but I did have a year or more of knowing I was trans/ passing feebly as male in public before going to therapy, so I don't know. Personally I think you should try to pass as soon as you can, it's the most awesome feeling ever

Your therapist, in my experience, can't write prescriptions unless he or she is a psychiatrist. Psychologists and Social Workers just do therapy, not drugs. Plus, you'll need to go to some kind of doctor to get blood work and physicals before you start T, to make sure you're healthy and to see your hormone levels so they know what dosage to start you on. Every doctor does it different though, so that's another question to ask your therapist.
I was considering informed consent and asked about it here on the forum, but I still don't understand it fully. I know that basically you have to know all the symptoms, and you have to be aware that there are possible symptoms we don't know about yet, like long term side effects.
WOW long post! Phew! Hope I answered some questions. Basically, everyone's experience with therapy is a little different.