Jr. Prom dress woes!!

Hey everyone, so its that time of the year again....
Yes I'm talking about PROM SEASON!!!

So as you may or may not know I am a junior in highschool and at my school we have junior prom..which is well..prom for juniors. I don't have a date but am going with a group of friends which will be awesome. My only dilemma is dress shopping. I really want to look and feel great and I know I won't be 140lbs come prom night(its may 21) but I do want to feel beautiful. I'm reallyyyy self-conscience about my arms. They're terrible =(. And finding a prom like dress with sleeves is next to impossible. I've found a dress that I really like but I haven't gone to the store to try it on and its rather expensive. I think its about $300 or so.

I love the vibe of the dress. So twenties! I love it. I'm scared though that it will be unflattering on my body type.

I love it in gold the best.