Let's assume you have no significant other issues, such as starting out as a professional body builder in terms of shape.
Assuming the above, in terms of passing, the three biggest things that I've seen that allow one to pass are:
- Facial hair removal
- Voice training/surgery
- Learning to behave as a female (undoing male socialization)
If you can get those three things done, you can pass, period. It doesn't matter if you're nearly flat chested.
After that, why do you need an order? Do what you need done for yourself and yourself alone.
Do you have major genital dysphoria? Aim for GRS first. Do you really hate the way your face looks? Aim for FFS first. Do you want a large bustline but have had almost no development? Get a BA done first.
For me, given that I have, on more than one occasion come close to self-harm over genitalia, my therapist and I agree that me seeking GRS first is the best course
for me. Further, as an older transwoman, and as a guy who didn't have an excessively male face, FFS is something I can wait on til later.
But you? You're the one who gets to decide what you do. Decide
for you first and foremost. Then go for it!

Good luck!