Good values at home are essential for children to develop well, And as you know, the example of parents is essential. One of the fundamental values for the development of your children and for society in general is that of gratitude.
Children learn to be grateful first when they don't get everything they want. This is essential, and therefore, it is necessary that you do not give your children everything they ask for, even if you can give it to them. You must do a good job of selecting and prioritizing what they can have over what they can't.
What happens when they get everything they want and ask for is that they expect everything they ask for. You may be a parent who says yes too quickly to children's demands, perhaps because of not listening or avoiding a tantrum, but this is a poor choice. This is not used for basic needs, of course, but for things that go beyond the essentials in life. They will be grateful for the things they get when you don't give them everything they ask for.
In addition, it is also essential that children learn to say 'please' and 'thank you'. Talk to your children about when someone gives them a good gift, that person (or their mom or dad) had to go to work to earn the money to buy that gift. Talk about how good it is to have generous friends and family because not everyone has that in their lives.
Make them responsible for thanking others, both verbally and in writing. When your child receives a gift, ask them to write a thank you note in return. It does not need to be long and eloquent. Just the practice of taking the time to write thank you and having the gift appreciated helps them practice gratitude. This is a valuable skill that will accompany you forever.
Thankful people are happier people too, so help your kids see that they should be grateful for the blessings, big and small, in their life.