How much $ to give as a college graduation gift for my niece?

well for my graduation I got a $100 visa gift card. $50 from my grandmother. It's enough to buy her nice brief case. But you could just send her a card and make them feel bad for not inviting you. But in all fairness they give limited tickets out for graduation, like for me it was 7, but I'm a twin so we got double so we got to invite everyone. I had two left over and gave them to another student that couldn't invite all the people they wanted to.