How can a racer with limited resources start creating content for sponsors using just a phone and basic equipment?

You don't need an entire production team to produce quality content. With an iPhone and basic editing skills, you can do a lot. Social media algorithms now actually favor phone-created content over highly produced content, giving individual athletes an advantage in reaching people. Start by building a content schedule with small goals and build from there. Once you get comfortable with platforms like Instagram, Facebook, Twitter, or YouTube, create more content around yourself - not just race results. In-phone editing is available now, and tools like Premiere work well. When ready to level up, consider a DSLR camera with interchangeable lenses to improve quality.