I just bleached my hair and it turned out brassy, do I need to tone it before I dye my hair purple?

You need to lighten the orange more. The orange will make the purple look dark and your roots look super vibrant (since its white/pale yellow). Lighten the orange until it is about light yellow. Then you'll need to tone it with a blue or violet toner. Leave the toner on for 5-10 minutes but watch it VERY closely. Toners can change the color of your hair to blue very quickly if you don't watch it.