I want to create a game.. What to do?

From as long I can remember I wanted to create games. I am a quite good story teller, at least that what my daughter say. Now I have been looking into things on how I can create games. I have tried unity, game maker and construct 2. First of all I just want to create a simple platform game, but the story for the game that I want to start with is stuck in my head and I feel that the story requires me to do lot of artwork. So where do I begin… 

1. Select the ultimate game engine.. done = going to use construct 2.

2. Create a prototype of the game.. not done. Even if the game engine is easy to use, I still need to learn how things work in the engine.

3. Create a sketches on how the game will look like… kinda done.. in my head. But I started a online artwork class so I can visualize and draw what I want. This will take some time.. I don´t think I can say I´am good at drawing. Well hopefully within 3 months time I could sketch some figures and environments.

4. Create music for the game…. Uhhh, yeah.. Let see how that one goes.

5. Sounds for the game.. Yeah same as number 4.

I don´t expect to get any money from the game, but hopefully if the story, artwork, music, sounds is good, maybe just maybe I can sell few copies on steam or somewhere else. This will require a lot of work and the only time I have is the free time on the evenings when I am not in the other work.

When do I begin ? Well, first of all I need to finish the artwork classes and see how that goes. When I finish that I can get to the next point which is learning the game engine.

I really do like critics on my work so maybe I can drop some sketches here and there on vivaldi.net and see if someone could tell me how the characters, environments, sounds etc. feels to them.