Bras are optional. It is about what each woman is comfortable with.
I have D cups and only wear expensive brand name sports bras. No underwire here unless I need a strapless bra, but by the end of the night I am so done with that.
I find a style I like and tend to collect every color they release for variety. Purple, pink, blue, black, white, grey, plain, stripped, etc.
Proper fit, support and comfort is key.