Some good advice from my end would be to puck a language and master it.
For game development, users mostly go for C++ because its the fastest run-time language. Also, a lot of game engines rely on it to function.
C# has a lot more libraries and general support -> But engines are much more limited.
Don't go big too soon. Having an idea for an MMO and trying to create it yourself will lead you to a shortfall. I've had first had experience with trying to create a team to do this too. As the pinned posts say - unless you have a lot of money (or are a game development studio), don't attempt that.
Start small, and work your way up. Allow yourself to grow rather than pushing yourself to be the best. Looking back now, I can see how foolish I was in the beginning...
This question has been asked MANY times before over various forums, and there is a lot of excellent articles on how to do so. Try googling how to get into game development. Learn what you need before you start.
The process generally starts with an idea. When you have it - work on it. When you finished working on it, leave it for a couple of days. Try to not think about it at all. Then, come back to it and see if what you've written makes any sense. If it doesn't, try again. If it does, bombard it with as many questions as you can. Try break the idea. If it withstands all that, then only start actual development.
When it comes to developing, try to stick to a cycle. You can easily loose track of where you are going after you start if you don't have a clear goal. Remember to keep your code clean and ALWAYS ALWAYS ALWAYS comment your methods, inputs and outputs. IF anything goes large, you WILL need others to help you. If your code looks look something I wipe off my foot, then you might as well give up.
There is so much more I could say, but most of it will come through your own experience.
But asking for help isn't weakness. The more ideas and opinions you get from others - the better. Flaming will happen whether you like it or not. Please try to counter it with some pride and enthusiasm.