Petite House Dresses What To Wear To A House Party?

What to wear to a house party? - petite house dresses

I'm supposed to be an event of the "campaign" with my BF (go all the boys came mustache include awareness of prostate cancer, and girls could wear fake mustaches).
And here is my Delem ... Of course I have no idea what to wear. The first time I was hot with my party BF if I should look. So the cause of my sis is going well, then they are the best friends n love to bits, we are the biggest rivals. So I know this dress is so hot.
Normally I'm pretty relaxed with my gear when I'm near my BF cause, so I just hang out rather than a rule. So I usually wear sneakers, jeans, sweater and shirt. But I like clothes too much, only what to wear my first opportunity for him, cause, and when we were with him when I was camping I saw all this dirty (even if he says otherwise: P). That does not bother me happy, but only for special occasions or the club in general.
How to be a party at his house. And even though I'm 20, I've never been in a real house party ... No ONCand Halloween. I really clubbing, but rare cause well, I'm not in that scene and not my BF.
So what would an elegant look sexy but casual look with a Hispanic (dark skin, long black hair and eyes), with a little character, and the average height?

Thanks for the help:)