Ranga Puja Etiquette?

[princess_peach]

I am attending my friends Ranga Puja in a few weeks and I have no clue about the occaision. I could tell from the fancy invitation that it is very formal and I know it is a big part of her life since she has been practicing Indian dance for about 14 years. I also know that it is a way of worshiping Krishna, but otherwise I am practically clueless to the culture of it as I am not an Indian or Hindu:

what do I wear to the preformance?
am I expected to bring a gift and/or flowers for her or her family?
does attending the dance entail any religious significence for attendees?

please leave any tips you might think helpful~
thank you!