Rewards need to be small. Children should not get expensive gifts, or large sums of money as a reward. Nor should children always get tangible rewards. You do not want to promote the sense that a child needs to be good in order to receive gifts. In fact, most tangible rewards have their greatest value in the praise that accompanies them.
Privileges are rewards that allow a child to experience greater freedom or opportunity.
Privileges might involve extending bedtime, giving extra play time, or allowing a child to borrow or sue a valued object. They are most effective when they are connected to the behavior being recognized. Increasing responsibility is similar to granting privileges. To reward children for keeping their room picked up, you may increasingly give them total responsibility for the care and cleaning of their room. You do not need me coming in your room.