I went full-time after about 10 months on HRT. Before then, I had been gradually easing my look more and more into androgynous territory, presenting female on campus, and stocking up on women's clothing but I balked at going all the way because I thought I couldn't do it. But after a while interacting with the world as a man was taking its toll on me and I decided I had to take the risk and be me.
I made it a point that, from the beginning of the 2014 school year on, I would be Rose for the rest of my life, I would abruptly stop wearing any items of male clothing in public, and I would complete my transition by changing my name and gender marker by year's end.
I did it. I'm almost 2 1/2 years on HRT now and more or less fully transitioned (though I'm still not ruling out bottom surgery). I pass well, even though I never wear makeup and never bothered (or will bother) with any sort of top surgery.
My $0.02 on FFS: It's not really worth it unless:
A. You have an exaggeratedly masculine face and have had extreme problems passing because of this.
B. You're starting later in life and unlikely to get the full benefit of soft tissue changes that come with HRT.
C. Your brow ridge and jaw contour causes you so much dysphoria that you won't be complete until it's gone (because that's a perfectly valid reason!)
But if you're just worried about passing, try without the expensive top surgery first! I'm a big woman (5' 10" and 230 lbs) with a beefy Scots-German frame. I'm not petite or gracile by any measure. But what I've found is that if you project a plausibly feminine deportment and grooming and can stand a messy trial-and-error process learning to work with what you've got, you'll save a lot of money and possible disfiguring complications by minimizing the amount of surgery you get done.
