My dream is to be an actor.
I dream of being an actor.
My dream is to become an actor/actress.
I have a dream, which is to be a singer and actor.
根据具体的语境和需求，您可以选择其中任意一种表达方式。例如，如果您想强调自己的梦想，可以使用“My dream is to be an actor.”；如果您想表达更广泛的梦想，包括唱歌和演戏，可以使用“I have a dream, which is to be a singer and actor.”。