One way to make sure that you have enough bandwidth to play online is to assign a higher priority to your platform in the network or a lower priority to others. You can do this in the router's Quality of Service settings. These setting allows you to control the download and upload speed for specific devices in your network by assigning a lower or higher priority. This way more bandwidth will be left for the device or task that is currently most important.
Additionally, some routers have a setting called Bandwidth Limiter. (It may be called differently in your router.) This allows you to put a cap on the bandwidth specific devices can use.
Be aware that priority settings may cut some low priority devices off the internet. If you need help to make the right settings or run into trouble, please contact the router manufacturer directly.