It depends on whether it's a high school or college graduation, and what the relationship is to me. We don't recognize any other graduations....kindergarten, middle school, etc.
We have two high school graduations next month. One if for twin boys...we are very good friends of the family and have known the boys since they were born. They will each get $100. We have another young man who we have gotten very friendly with over the past year...he will also get $100. When dd's friends came to her graduations parties, some gave gift cards (for small amounts) or small gifts.
When it's family, all bets are off! Both my dh's brothers were very generous when our dd graduated. She got $500 from each of them when she graduated college two years ago! So, of course, when our nephew graduated last year, we had to reciprocate!!! Good thing, for us, he is the only other child in the family!!!
So, I guess it's up to each person to decide. If it's just a friend of my child's, they get $50. If it's a good friend of our family, then it's more.
I think one of the best high school graduation gifts my dd got was a huge laundry bag, with her initials embroidered on it, with two rolls of quarters, detergent and softener sheets in it!!