One of the first things you might want to do after surgery is go out an buy yourself a new bra. But realistically when will you be able to know what size to buy and wear it?
After surgery you will be in a post op bra which is like a crop top. You will be swollen and tender for a few weeks and it is likely you will need to wait a few months before your breasts are stable and then investigate a new bra waredrobe. Before then it is best only investing an an inexpensive bra and usually something that is comfortable like a sports bra or something without underwire. Most women see the swelling subside within 8-12 weeks.
Just think, you will have plenty of time to shop for your ideal bra post opp but the first couple of months are all about comfort and reducing the swelling with soft stretchy material.