My advice as a girl who's had many different hair lengths over the years (even as a guy):
A) Go to a proper hair stylist. Someone who knows what they're doing. I.e. not one of the "cheap shops". With hairstyles, it's my experiance that you get what you pay for
B) Tell them that you intend to grow it long, and even mention that you want to look more feminine (you don't have to tell them you're trans*, just tell them you prefer a more feminine look). If you can find a pic of the hair style you're ultimately aiming for, it will help explain
C) After explaining what your aim is, ask them to trim it. It will take a little off of course, but tell them to keep it as long as possible. The aim is to get rid of split ends etc while not setting yourself back too much. By explaining you goal in the previous step, thy will (if they're worth their salt as a stylist) give it some shape to help it grow out the way you want it.
D) Let it grow out more, and book another "tidy up" appointment with the same stylist (same place, preferably same person if you can) around about the time it starts noticeably fraying at the ends again.
Hope that helps babe

Obviously doing this will take a little longer than if you just let it grow wild, but it will keep it looking reasonable as you go along
♥︎*Hugs*♥︎