Baby birthstone jewellery

I needs some help. I'd like to get something made for my little one that I can give them one day. Iv decided on jewellery. If it's a girl I'll give it her on her 21st or wedding day and if a boy I'll give it his wife on his wedding day. So do you guy have any pieces I could see. I'm having a had time picking between a ring or necklace. Our baby is October so we will go get it made on the 1st before they are born. Thanks for the help just need some inspiration !