For someone who is only 15 years old, my biggest suggestion would be to do something you enjoy, no matter what it is. I didn't have my first job until the summer after my senior year of high school and didn't have a business related job until the summer after my sophomore year of college. The key is building a skillset that you can carry over once you graduate college and are looking for a full time job, but you still have plenty of time for that and you'd be surprised the skills you can learn from the activities you love. For myself, I was always into sports and the skills I obtained from playing sports such as thinking quickly, working well with a team, communicating effectively, being a leader, and learning how to handle pressure are all things that help me with my job everyday. At this point I would say focus on building versatile skills that can be used in any industry and continuing to try different things to determine what you are most passionate about.