dance party

In my life, I have never been at the dance party becasue in Japan we do not have that custom.
This Friday I am to go to the dance party at the opera house so I need to prepare.
The party is only 7 pound.
I think I am so genius to find this event.
I have never been at the party so I do not have much idea.
What kind of wear I shall put? Is it ok even if I do not know the steps?

I called to the Opera house and asked what kind of wear I shall put.
The person at the Opera house said that "Not too formal and not too casual".
Well, it is too difficult.
Actually I have a formal dress in my closet.
I brought it from Japan because I thought I had a chance to wear that kind of dress
but it turned out not. I got this dress at NY at the price of 25 ￡ but it actual price should be 350￡. You can guess how my dress looks like.
Actually I want to wear it but the person on the phone said that"not too formal".
I asked him if I wear a formal dress, it could be a bit too much and wired or not.
He said it depends on the person and the dress.
I completely understand him but ....
So today, I checked the dress in "Monsoon" on my way home.
I could not resist because it is so cute.
I am not supposed to buy the dress because I am a poor student and I have a formal dress.

My friend said that there must me a lots of old people there.
I think it is right.
Never mind!!
Even if my first and last dance perty is the one without young people.
In this way, I try to be positive but
I might not go to the party because I do not have cofidence to be there.
I hope I am brave enough to try.