When you are starting out, adding other people’s pins can help you attract an audience faster than having empty boards with no pins. If you have a good amount of content of your own (such as 10-20 pins or posts), then you can just save your own content as well.
Once your account starts to get some traction, you can focus on just saving and pinning your own content. Pinterest is not a zero-sum game so you needn’t worry about loosing traffic to your competitors.