Which scene of The Tempest would be easier to write for creative writing?
It depends a lot on what you have to write about. What is the topic that you have been given and what advice has your teacher given you? There are lots of possible tasks that you could set yourself. For example, it would be really interesting to write an account of the storm as depicted in Act I scene 1 from the perspective of somebody on the ship, or to write an account of Miranda's life from her point of view after her father has told her more about her history and past in Act I scene 2.
Another idea would be to focus on one of two of the more bizarre characters in this play. What would Caliban or Ariel say about the play and the action that goes on in it? This would be a great idea for creative writing as you would have the chance to give these characters, who are both oppressed by Prospero in different ways, their own say about what happens.
There is plenty of scope for doing very interesting pieces of creative writing. I suppose the best advice I could give you would be to think of what you like most about this play, whether it be a particular character or a particular section, and base your creative writing around this. Your own interest in the topic will be something that will help you write a more convincing piece of creative writing.