Next time go early, walk around and figure out where would be some good vantage points to shoot from. Look at the backgrounds, if you take pictures standing in a particular place what will the background look like? Get some test shots if need be to figure out camera settings etc. so you're ready when the event gets going.
Try to get shots of individuals or small groups in closer, or scenes with some people dancing, or maybe a few at tables, etc. You don't want people chopped off (look at the sides of your photos) - either get them in the frame and in the photo or out of the frame and out of your picture (or when you crop them down think about where to crop). You need to get people's feet in the frame too.
Keep distractions out of the frame (#7 & 8 lower right), objects or edges of objects and people that don't need to be there, that aren't part of the scene or adding to the picture.
Maybe you need to spend some time not taking pictures but just looking thru the viewfinder and thinking about what you see, what's in the frame. It seems like you're seeing the person/subject but not necessarily what's behind or around them that will be in the picture.
Shooting events is timing too, wait a split second til for example the one girl would have turned her head so you'd see her face in profile instead of just hair. Watch as they're dancing, is there a time as they repeat moves when they turn or move a certain way that would make for an interesting picture.