I have spent years teaching my girls good manners. I am constantly telling them that manners don't cost anything and they mean so much. I am a little bothered when I notice that some people are skipping basic manners.
I have taught my 7 and 8 year olds that when you receive a gift, whether you like it or not, you give a big smile and thank the gift giver. They know that the gift is not as important as the thought that went into it. You are thanking the gift giver for their time and thoughts too.
AND, you never, ever complain or say ANYTHING negative about the gift.
There are nice ways to say thanks but no thanks.
If you receive a gift bag, thank the relevant people.
Use a hashtag to link it back to them.
and please don't bitch or complain.