For my high school graduation, my aunt gave me a very nice gold cross to wear as a necklace, and she said it would bring me good luck if I wore it. Is she right? — A.McP.
I'm sure your aunt is sincere—but no, she is not right. No piece of jewelry (or any other object) has any power to help us or bring us any benefit.
In fact, the Bible specifically warns us against putting our trust in "good luck" charms or objects of any kind. Such things were very common in the ancient world, because many people were very superstitious in those days (just as many are today). But the Bible says, "This is what the Sovereign Lord says: I am against your magic charms" (Ezekiel 13:20). Only Christ has the power to change our lives, and we are to put our trust only in Him.
This doesn't mean it would necessarily be wrong for you to wear a cross—if you do it for the right reason. Centuries ago, Christians used the image of the cross to identify themselves as followers of Jesus, who had died on a cross for their salvation. I wish it had the same meaning today—although I know that for many people it is only a meaningless piece of jewelry.
We should never see a cross without being reminded of Jesus' suffering and death for us. The Bible says, "Let us fix our eyes on Jesus, the author and perfecter of our faith, who for the joy set before him endured the cross" (Hebrews 12:2). If Jesus was willing to give His life for you, shouldn't you be willing to give your life to Him? Make your commitment to Christ without delay.