P.S. If you find all that confusing, let me try again: it is not true that there is only one God. As you originally observed, Jesus and his Father and the Holy Ghost are all Gods, and they are three different people. When Jesus told the Jews he was the Son of God, they accused him of blasphemy, and he said, basically, "In your own scriptures it says you are all gods. How can you say I'm blaspheming then because I say I am the Son of God?"
31 Then the Jews took up stones again to stone him.
32 Jesus answered them, Many good works have I shewed you from my Father; for which of those works do ye stone me?
33 The Jews answered him, saying, For a good work we stone thee not; but for blasphemy; and because that thou, being a man, makest thyself God.
34 Jesus answered them, Is it not written in your law, I said, Ye are gods?
35 If he called them gods, unto whom the word of God came, and the scripture cannot be broken;
36 Say ye of him, whom the Father hath sanctified, and sent into the world, Thou blasphemest; because I said, I am the Son of God?
He's referring back to Psalm 82:6, "I have said, Ye are gods; and all of you are children of the most High." So anyway, the simplest and most basic true answer to your question is, "It is not true that there is only one God. That is an old sectarian notion and is false."
Rock Is Dead. Long Live Scissors!
"The presentation or 'gift' of the Holy Ghost simply confers upon a man the right to receive at any time, when he is worthy of it and desires it, the power and light of truth of the Holy Ghost, although he may often be left to his own spirit and judgment." --Joseph F. Smith (manual, p. 69)