What is not op mtf

What can I wear as a trans girl? MTF?

Since you probably haven't had an operation before, I would recommend tucking underwear that will help you hide your genitals. There are various parts to buy on the Internet, also on sites like amazon, but there are also special web shops that mainly specialize in this (e.g. www.trans-missie.com).
Of course, you can also wear silicone breasts if your breasts have not yet grown so much due to the intake of hormones. There is also a larger offer on the Internet for this. Both on silicone parts and on special bras for it. But with 2 sports bras they are just as secure ;-)
If your breasts have already grown a bit, I would recommend push-up bras to make them look bigger and in better shape ^^

Otherwise you can generally wear anything you want.
Take a look at what you find beautiful in other girls / women and let them inspire you.