I've read mixed reviews on whether or not bras are good for you or not. A Google search online and you will find back and forth reviews, and research stating one way or another. It almost feels like there's new evidence that says it's fine, or no it's bad. It's really enough to make your head spin.
Personally I like to wear a bra in it helps to hide my nipples that almost always seem to be erect, and now even more so as I progress through NBE. Sure I guess I could wear pasties and such, but I guess part of me likes the idea of wearing a bra as well.

Besides, I would have to wear at least three layers of clothing to try and hide my nipples, and that gets hot and uncomfortable very quickly.
If you do decide to go for a bra, finding your bra measurement isn't easy. Sure the band size might be something easy to find, but the cup size will vary. Varies by style, brand etc. Even the band size can be a pain from brand to brand. The cup sizes are harder to figure out on a genetic male. I have yet to find any site to give a good way to measure cup size for a genetic male. Nearest I can figure I am somewhere between a 36AA-36A, and that's measuring at 36 under, 39.5-40 around the center. Figured my cup size mostly by trial and error.
Hommemystere website carries bra's that are more fitting to a biological male. Unfortunately not a lot of options for larger cup sizes.
I think currently the research is pointing to bras being bad, of course, it will probably change again.

So it may just boil down to your personal preference, and if you feel it is necessary to prevent any possible chaffing during your development.