Hello,
Welcome to Microsoft Q&A!
First, we are very happy that you are interested in developing Xbox games. To start your development, you could go with Developing Games for Xbox. This is an introduction to Xbox game development. Then you could learn something about Xbox Live - Getting Started with Xbox Live. It shows what is Xbox live and how you could use it. After that, you could Joining a developers program to decide what do you want to develop and what platform that you could choose.
Thank you.
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