Cheerleader

 
To see a cheerleader in your dream represents competition and triumph. Your dream may be telling you to offer more praise and encouragement toward others.

To dream that you are a cheerleader signifies your self-confidence and self-esteem. You need to be more active and more positive in some waking situation in your life.

Someone who provides encouragement, enthusiasm, or motivation
An athlete, or an athletic activity in your real life 
Activity that you or someone else considers secondary or "on the sidelines

You or someone else that is supportive of others goals. It may also reflect being happy for someone else success.

Alternatively,may represent self-encouragement or self-motivation. A sign that you are optimistic and confident. You are telling yourself that success is possible.

Example: A girl dreamed of  at a sleepover. In real life her friend abandoned her when she got a boyfriend. at the sleep over reflected her attempt to be happy for her friend while being forced to notice her own single life.