Although Internet of Things (IoT) networks are massively deployed in many different areas, there are significant problems regarding the network topology and capacity, due to low smartness level of IoT devices and cost matters. Congestion and queue management especially in an IoT network buffer is one of the most important subjects that need to be considered. In this paper, we propose a novel game-theoretical approach to manage the queue and avoid possible congestion, by adding a little intelligence to dumb nodes with a lightweight method called AQM-of-Things (AQMoT). Extensive-form game formulation is used for defining decision making criteria of both IoT nodes (when to send) and gateways (when to drop). We describe a game model according to the queue level as well as other network conditions. Thus, a novel congestion avoidance method is proposed, where senders care about the gateway's current situtation with a very lightweight game theoretical algorithm. We also demonstrate a conceptual comparison with alternative queue management approaches, and conclude that the proposed AQMoT approach has important advantages especially in IoT domain.