Reward people commensurate with the achievement reached.
When a person makes a significant achievement make sure you give them the most appropriate level of gift that fits the level of the performance reached. For a small achievement instant recognition is often very affordable which enables you to recognize people more often. For a much larger achievement select an award that is most symbolic and meaningful of the behavior you are recognizing an individual for. Or acquire a gift or reward that has a much higher value than a small gift of appreciation.