“Don't be wasteful. Let's donate them.”
You and your husband have some old clothes and children's toys that you don't need any more. Your husband suggests throwing them away. You don't like that idea because it's bad for the environment and because you think that someone else might still want them. You say this.
Don't be wasteful. Let's donate them.
The expression "Don't be ___" is useful for when you want someone to act differently:
Don't be silly!
Don't be so sensitive.
Don't be angry at me, please.
Don't be selfish.
You call a person "wasteful" when they throw away things that could be used again, or when they buy things that they don't use.
Just use what you need. Don't be wasteful.
You can also use "wasteful" to describe a person's actions instead of the person themselves:
Using paper plates and plastic cups all the time is so wasteful!
To "donate" something means to give it to a person or group that needs help.
People donate things to individuals whose houses have burned down, to churches, to homeless shelters, and to thrift stores. Things that people can donate include:
donate used clothes