S.H.
is $50 a usual amount for you to spend? Seems excessive to me. :) My sons received $20-25 when given cash at their Communion. But NJ costs a lot more than the Midwest.
That said, I have always preferred avoiding cash gifts to children. Hit a Catholic supply store online & take a look at what's available. Lots of options, just be sure not to duplicate the more popular ones....cross necklace, etc.
Dress code: it's a church service! The Communion participants & their families will be dressed up, but it's basic "church" clothes for everybody else. Reuse those Easter outfits if you have them!
& if you're not attending, then send a Communion card with a gift card in it.
First Holy Communion is a wonderful & uplifting experience. If the priest is child-oriented, it's even better!