1 John 1:3 (CSB) what we have seen and heard we also declare to you, so that you may also have fellowship with us; and indeed our fellowship is with the Father and with his Son Jesus Christ.

It is our testimony (what we have seen and heard) that we need to share with each other. Not just our salvation testimony but how we see God working in our life today and yesterday. That way we can share in a common fellowship. How can two men walk together in unity unless they know the direction they are walking (Amos 3:3). A strand of three people are stronger than one Lone Ranger (Ecclesiastes 4:9-12). When two our three gather with God in mind that is when fellowship happens (Matthew 18:20). It is good for Christians to gather to have fun, for the world aught to see us having fun in Christ, but make time to share what God is doing in your life or at the very least ask questions to learn about your brother or sister or God! If we all have a little bit of fellowship with God and Jesus than we aught to have something to talk about with our fellow Christians. Fellowship with God and Jesus happens when we pray to God, praise Him and read His word.