"I'm going to go home" sounds like your intention. For example, if you don't want to stay at a party any longer, so you might say to your friends "I'm tired. I'm going to go home now". You could also use "I'm going home" in this situation with the same meaning. An additional meaning of "I'm going home" is for a future arrangement which is already scheduled. For example, you might say "My course ends in June, and I'm going home in July". "I'm to go home" is different. You would use when it has been decided - by a person or people in authority - that this is what is going to happen. You have been given orders to go home. For example, you might say, "The doctor says that I'm to go home and rest."

I'm going to go home - same meaning I'm going home.- same meaning I'm to go home tomorrow ( scheduled )