IN THE BEGINNING
First, we must attempt to understand GOD, the Supreme Being, the Ancient of Days, the Father of us all. We need to understand God's history, His future, His purpose. We must try to comprehend His desires. We must attempt to see the Universe from His perspective.
Without a doubt, great, is the mystery of God. He says things in the Bible like "I am the Lord, and there is none else, there is no God beside me:" A vision is given to Daniel the prophet, where he sees the "Ancient of Days," God the Father. He has made us in His image. He has created all things. He commanded and the creation came into being. We cannot completely comprehend Him. His Son is before all things and holds all things together.
(1 Timothy 3:16; Isaiah 45:5; Daniel 7:9-10; Genesis 1:27; Psalm 33:6-9; Job 37:5; Romans 11:33; Colossians 1:12-17)
Before God / After God
He says in the scripture, "I am Alpha and Omega, the beginning and the end, the first and the last." (Revelation 22:13) God is the Creator. Before He created, there wasn't a creation. He was not the Creator until He created. He always was the only Creator who could create. Time was not. It was His time. It is His title. Creation is God's prerogative.
He is the Only One who could create, and thus become the Creator. The Creator had just not created yet. He was thinking. He is God. It doesn't matter to me. I wasn't around. God didn't ask for, or need, my advice.
He was always God, God the Father, The Ancient of Days. God the Father, with His family, the Spirit, and The Son, They always were. They are. They always will be. This is hard for mortals to understand. There will be no after Them either, for They are, and uphold all things.
Then They began to create. Creation is God's pleasure. Creation is God's responsibility. Creation is God's job. It is His title. He is the Creator.
Aside from the creation of this earth, no human record is kept of what else in the universe God created, or what He created first. Many speculations exist on this matter. It isn't known how long God thought about creation before He started, or how He did it. We do know "Through wisdom and power God created the world." (Jeremiah 10:12 paraphrase)