So we turn to Mark's gospel. Mark 1:1 "The begining of the gospel of Jesus the Christ, the Son of God."
In our attempt to avoid the Trinity we find that God's Saviour (Jesus) is the Christ (the one anointed by the Father with the Spirit), and is the Son of God (the Father). He's also swiftly announced to be the Lord coming to live among us, the Spirit-baptiser and the beloved Son...
Matthew fares little better - Jesus is God with us, and by the time his book is done this Jesus is sending people to immerse people into the name of the Father, Son and Holy Spirit.
And as for Luke, Jesus is the Son of the Most High, the beloved Son at his baptism, son in his genealogy, temptation and his prayer life... to give just a few examples.
And books like Genesis tell the same story - In the beginning, the God with a Word who goes out by the Spirit...
Trinity isn't the obscure bit of Christian theology once you've got your head round all the big Omni-words about God. Trinity is the whole thing. Less, the One Big God who somehow is three... but rather Three who are United in love, observable as they relate to another.
Omni-God's fall over against the big questions of our culture. How can a God of omnipotence not stop suffering... Trinity says - God comes near, to heal and teach suffering men, and to suffer for with and for us (see Athanasius, On the Incarnation). That may only be the beginning of an answer but it gets things beyond whether God can make a rock too heavy to lift and on to his personal introduction to us.
In Luke's account Jesus prays to his Father, full of joy and thanksgiving in the Holy Spirit. He tells us that only he knows his Father, and only his Father knows him. But, his Father has entrusted all knowledge of himself to his Son, and so the Son is at liberty to make his Father known. Which he delights to do... like when Mary sits at his feet to be taught.
The heart of Christianity is the Son's relationship with the Father, as Donald Fairbairn puts it. And by the Son's incarnation, death and resurrection we enter into this relationship. We come 'in the name of Jesus', our names written in heaven - where the Son stands with his Father.
The early church were clear, if you are to say anything about the Christian faith, it's Trinity that you must talk about. Other religions go for Omni-gods - like Islam. Or against Omni-gods - like new atheism,.. But I can't get past the Father's Spirit-filled Son, Jesus.