This is going to be offtopic, im really thinking about closing the Thread.
WELL!
Here are my Tips.
Wait with it, learn first. Then decide if this is worth it.
You are very young, and youngsters like you are being very enthusiastic. This is nothing bad at all, but the thing is this: You see what others have made, you think it cant be that hard, they made it without being Pros. Well, yes, BUT they learned stuff about it. For many years. They started very little, making it their hobby/work.
For example, FH tooked over 1 Year from nothing to what it is right now. With constantly working on, every day improoving, reading back the code, testing.. and so on. And the creator of FH has lots of experience since he made Impressive Title bevore. Still needet over 1 year. And to be honest, 1 year was FAST, very fast.
You need to know on what Operating System your game should run, which enginge you want to use for it, which format your files should get, which 3D programm is the best for you (do not count on prices). Then you will have to think about the Soundsystem, will it cooperate with your engine? Do you have a strong Server, do you even know how to set up a Server to handle a multiplayer game?
Then modelling... are you good in it? can you low poly model? (High poly laggs) Can you set the ARmature right, can you assign the bones right to the model? Can you animate it properly? Can you connect the animations to the game engine properly? And so on...
I am not trying to destroy your buble, i just want to open your eyes. If you want to do somthing good, then first get s much information as possible and learn.. learn.. learn.. and also.. LEARN!
The Rest is already sed by the previous posters.