I would suggest going to an upper end lingerie boutique and see if they would fit you in the right size and type bra. A very high percentage of women, not just trans women, wear the wrong bra size. Many people do not understand that when your weight changes your bra size will probably change as well. Immediately after I had my breast augmentation 14 years ago I went to a very nice boutique where I was fitted. I have continued to buy my bras from that boutique since then. When you start wearing a bra everyday, be it before or after breast augmentation, I would spend the extra money and get a couple of bras that are fitted for you and that are comfortable and easy to wear for long periods each day. You will find out very quickly that the band is perhaps the most important part of the bra as, if fitted properly, you will not have it riding up on your back. If for no other reason, you also want the right size and type bra because your clothes will look much better on you. Other women notice things like that! Clare is correct when she says that you want to stay with one bra maker as you will find their sizing consistent regardless of the type bra you are trying to find. Although they cost a lot more, I only wear Prima Donna bras as I know that what I am getting is going to fit, be comfortable and, if I hand wash them, last a very long time!
Good luck! Getting the right bra is not just about breast projection.......it is about comfort!