Generally a 1.5mbit connection with low pings will be enough, during a multiplayer gaming session, the voice chat generally uses more throughput than the actual game related data. What is most important, is your ping.
If you have other people also using the connection, then I recommend at least 10mbit/s and QOS rules in order to ensure that services like youtube do not cause issues for your games. (multiplayer gaming is not bandwidth intensive, but it sends and receives a lot of small packets, and needs top priority so that those packets do not end up delayed due to your limited low throughput. if you have a connection of around 30-50mbit/s then no QOS is needed for you to game and for other family members to stream from youtube while also even watching netflix, those services never hit high enough speeds to ever fully occupy the connection.