
Man, am I a cheapo?!?!?
Maybe it's just the area I'm in, but my dd had First Communion last year and received $50 and a sterling silver bracelet from grandma & grandpa. The god parents (and mom and dad) gave more, and we went out for a nice meal -- but that was the extent of it. No big party, so friends didn't give anything.
However, our church/school really advocated that First Communion was about the sacrament, the true meaning of the day over the fancy dresses and parties. Maybe we took it too literally,

but I know her classmates had the same type of day.
Well OP, I'd give cash. It's the amount I'm unsure of.