L.U.
Married to a Mexican man for the past 10 years, have gone to about 20 quinceneros......
There is no "acceptable" amount!! You give what you can. You buy a pretty necklace, you give money, you give a gift certificate. It is a huge deal for HER, but it's really just a birthday party. It's like a sweet 16.
So, go to the mass, give her a sweet card about growing up, and pop a $20 in there if you don't want to buy a little gift.
L.