Do I need to wear ankle braces if I haven't had any serious ankle injuries?

No ankle braces. Unless a physician has recommended that you wear ankle braces to protect against repeated injury/sprains, ankle braces are not indicated.
No. If you have no history of injury, bracing is not required. If you are participating in a sport where ankle injuries are common, you may consider prophylactic bracing such as "active ankles." this may decrease the incidence of ankle injuries, but these cannot completely prevent an injury.