Wooden nickels
This idiom or expression means:
Fake money.
Fake anything.
When someone says “Don’t take any wooden nickels, they mean:
Be careful;
Don’t trust everybody;
Don’t get taken or fooled;
Be careful in your dealings with others; etc.
History:
In the old days, wooden nickles were sometimes issued by businesses as a promotion and didn’t have a universally accepted monetary value. The warning above has now become an expression.