I'm thankful you want to believe in God–and God wants you to believe in Him, because He loves you and He wants you to be part of His family and walk with Him every day–even if you can't see Him.
Why can't we see God? Think about it this way: If we could see God, then He'd be just another object, like the moon or the ocean. But if He were just another object, He'd be too small to be God! Even if He filled the whole universe, He still would be too small to be God, because God must be far greater than that. King David in the Bible once exclaimed, "The heavens, even the highest heavens, cannot contain you" (2 Chronicles 6:18).
The Bible tells us instead that God is a spirit–that is, He is a spiritual being, not made out of molecules or anything else you can see or touch. But that doesn't mean He isn't real! In fact, He is more "real" than the things you see around you, because eventually they will disappear–but God never will. The Bible says, "I the Lord do not change" (Malachi 3:6).
But the most important thing I can tell you about God is that a little over 2,000 years ago He did something we can barely imagine: He came down from heaven and became a man! The invisible God became a visible person: Jesus Christ. Of all the people who have ever walked on the earth, He alone could say, "Anyone who has seen me has seen the Father" (John 14:9). Why did Jesus come into the world? So we could know God and have our sins forgiven. Ask Him to come into your life today, and He will.