We do you have to offer to the group? That question starts with your skills and experiences. But the question of your potential service to the group also needs information about the rest of the group. With one group of workmates, you may need to be one type of person. With a different group, you might need to be very different type of person. Sometimes you will lead. Sometimes you will follow. In some groups, you may need to do a lot of production. In others, your contribution will mostly be supporting others who do the actual production. There is no way to decide this in advance. You need to work out group roles within the group itself.
One way to look at this is to consider an old formula for business success: find a need and fill it. Another way to put this is, make yourself useful. Take a look at each member of the group and ask yourself, what does each of them do well? What do each of them wish to contribute to this project? What are they excited about? What experiences do they bring to the project? Then, after you have considered the skills and interests of each other group member, ask some more big questions: What are we lacking? What is going undone? What have we forgotten? If you are having trouble seeing where you should fit into the group, consider all these blank spots. If you can identify what the group is missing, then ask yourself, can I be that person? Volunteering to take the jobs that nobody else wants can be a great learning experience! For one thing, there is no pressure. Nobody will be fighting you to take your job away. You can just do the best you can and others will probably be thankful you are doing the job that none of them wanted. This gives you a chance to test out new skills and grow into them a bit. Remember, the more different skills and experiences you can put on your resume, the better it will be for you. You can always increase your skills and experiences by finding contributions that go beyond what others are willing or able to do.