V.B.
We are not RC, but Lutheran, and when our kids were confirmed they mostly received cards with cash (or gift cards) in them. Nothing extravagant, but a gesture... $10 or $15 or whatever.
Many children receive gifts of jewelry (rosary beads, crucifix necklace, etc) or such, but from what I have seen, those mostly come from family or someone close to them in the church. For us, first communion and confirmation is the same time, so it may be a little different in the RC church when they are separate events (they are separate events, right?)
As a friend of the family, rather than family or mentor/teacher in the church, I would give a card with cash.