Appropriate wedding gift and dress

In May I will be attending a wedding in Shanghai. The bride and groom are both Chinese. I am an American friend of the groom's. What is an appropriate gift for me to give? Also, I was planning to wear a red dress because I know that means good luck in China, but I was told the bride wears red. In this country it is inappropriate to wear the same color dress as the bride. Would it be inappropriate for me to wear red? What is appropriate?