There are hordes of people who want to become backing dancers. I’m sure you’ve heard of audition queues spilling out onto the street and around the block in some cases.
The fact is there are a lot of people competing for those handful of chances to become a backing dancer. It may seem quite daunting for someone starting out in the industry but it’s the way the industry is.
Of course if you’re a girl it’s worse as there are many more female dancers than male. This of course makes it even more important to stand out.
And I believe that is the key - to stand out. There are many ways to do this but you need to stand out in a way that is unique to you and offer something others can’t replicate.