NOTHING IS ORIGINAL EVERYTHING HAS BEEN DONE BEFORE HELP IM EXISTENTIAL
^ me having one of my many breakdowns trying to compose for music
I can assure you, not everything has been done. Brainstorms might not work for everyone but they're a great place to start. Take the concept of a 'Journey' and think about what it means to you.
Is the journey physical? Does it go one way or does it turn back? What changed because of it (or did everything stay the same)? How long was it? Was the effect of it immediate? When did the effect occur - during the journey, immediately after, or was it a delayed response due to retrospect?
Keep making up these sorts of questions for yourself and answer them. Once you have a conceptual understanding of what you want to write about, then think about ways to interweave that concept into your writing.
It doesn't have to be an extremely convoluted plot, sometimes basic and simple is better.
A man has to make a decision, and in his dream he makes one choice and it plays out in some way. How did this affect his decision later on?
A snail really wants to cross the road to meet his friend, but it's such a long trip that he gets fatigued half way through. What thoughts go on in his mind, and how does he find the will to finish crossing the road? Maybe he just decides it's safer to turn back.
Don't be afraid to experiment with what you write, it doesn't have to have a deep philosophical meaning. Make a list of ideas, pick your favourites and write them into full creatives. See which ones you like best and discuss them and their potential with your teacher. Experiment with writing styles, narrator types, first vs. second vs. third person, etc.