Even though it's not sending people to space or revolutionizing medical science, game development is still really cool. There's a multitude of platforms you can use, like Scratch, if you're a baby, or Unity, if you're based like me. The first step? An idea. You need something to base your game off of. Got it? good. Now, get basic things implemented. Don't focus on graphics or polishing anything, just get movement and basic features. Done? Add more detail to the features until you have a player that you're happy with. After this, you can upgrade certian assets (map, weapons, items, etc) and add certian details.