Evolution is indeed not linked to the creation of Earth. Evolution applies to living things and Earth is not a living thing. That was the easy part.
You also want a scientific, plausible explanation of how everything started. That is the hard part but let me point out first that everything doesn't need to have a start, some things could have always been. You believe this about God. I am not sure if I believe this for the universe or "everything", but it is a possibility.
This is as far as I will get with answering your question, because there are some problems with giving a scientific answer to your (and presumably several billion other humans') question. Science comes up with an hypothesis and then tests this to see if it could be true. The testing part is extremely difficult with hypothesis that handle about the beginning of the Universe as you probably understand.
That is why there is no satisfying answer to your question and why there maybe never will be one.