yes, the Hebrew letter "chai" is 18 and means life and multiples of are used a lot. Gifts......cah and gift cards are popular. Since before the era of gift cards, I have used travel sets (cosmetic or shaving). Depending on how much I want to spend, I might include cologne or a gift card to Ulta,etc.
If you know the parents well, ask them what their child wants. Even if it cost mosre than you want to spend, you can give them a gift card toward the item from an appropriate store.
And I think we are all trying to teach our children that it is "presence" not "presents" that is important.
An appropriate greeting is "mazel tov" which means congratulations.