I'm thinking of giving my youngest child nothing for his birthday to teach them about being materialistic.
That's a bit drastic. Why would you give your youngest child nothing?
I just have a difficult way of showing love to my kids so I usually spare them from material things.
First, why just the youngest child, that's extra mean if their siblings got gifts and not them. Furthermore, it's rude to not give gifts because YOU don't like material things.
If anything it's worse to give kids too much!
Children really look forward to getting some kind of gift for their birthday, and this plan will make them feel forgotten. You don't need to give them some huge over the top gift. Something small and meaningful will make them happy.