If you have trouble with creativity, think of it as a formula response. My teacher says that there are three aspects being assessed in the AOS writing section:
1. Your understading of the concept of journey. So make sure that the story is about a journey and that it has something to say or a perspective of the journey to communicate. Don't write the cliche of the "Year twelve journey", too many people do that, markers get bored reading the same thing, unless you have a very fresh perspective.
2. Voice. This is the way you tell the story, how well you communicate its meaning and the effectiveness of your voice. Don't write from the perspective of an animal or a child unless you are really experienced because the sophistication of your language will not be as high.
3. Craftsmanship. This is the devices you use to convey the concept of journey, such as similie, metaphor, and aliteration (there are heaps more). However it is also how well the writing piece flows together. Paragraphing, punctuation and spelling are also important.
Most importantly, I think that you need to write from the heart. Personal experience is a good idea, and you could also explore a personal experience through an extended metaphor or talk about an imaginative journey or an inner journey you have experienced.
Make your beginning and end very punchy, it will make your overall piece very catchy, and use descriptive and sensual (as in appealing to all senses, talk about smells, sounds and tastes as well as what you can see) imagery.
Write often and edit and evaluate everything you write, but don't throw it out if you don't like it. Practise is the key, you don't have to write a publishable writing piece in order to do well.
Good luck!