Remember FFS is for yourself and passing, but SRS has LEGAL implications. Basically you can change your sex/gender markers with government bodies along with name markers. If somebody asked my opinion, SRS first and foremost for this reason alone. This is speaking as an attorney. Because if you get SRS out of the way, it can cause less harm if there are problems at work and you are looking for a job.
Also it would be a good idea if you do get SRS to seek the advice of an attorney that has experience in transsexual document changes.
Some say that passing is key. But the truth is self acceptance and being legal is key. There are alot of TS out there that cannot pass, but they are legally female and they get by fine.
FFS is extremely expensive, painful, has an even longer recovery time than SRS, and honestly the only benefit is passing. I would say if you want it make it a priority after SRS if you think it is necessary to pass. Remember SRS has other benefits that FFS can never offer, it is the ONLY thing that will make you legally female.