I'm attending a wedding next month, and I've never attended one before so I'm a little lost about what to wear

I know nothing too revealing, and nothing white, that's it

So I went into a store yesterday, and I was found a couple dresses I liked, and went to try them on. I wasn't sure, so I started talking to one of the girls who worked there, and she helped me decide on one dress, but now I'm a little unsure again

It's all black, and floor length, and no sleeves

The girl helped me dress it up a little with jewelry, so it's not so black, so I got a long silver necklace, and half big silver hoop earrings.

Is black appropriate to wear to a wedding? Or should I get something else?

I decided to post a photo, despite it not being good quality