Start working on an indie game. Along the way, record Unity tutorials to begin building an audience. Post some texture packs to the Unity asset store, then some level packs, then some rigged and animated characters. Share some footage of test gameplay. Start getting audience feedback and fans. Release plot notes on the web. Maybe turn some of that into books (Infinity Blade) on Kindle & iPad, where the cost to publish is zero. Release the full base game as an open beta, but charge for it. Release the final base game at a low price or as free to play. Charge for DLC (Civ VI, StarLink) or skins (Rocket League, Fortnite), or a single player campaign (Halo). Twitch stream your gameplay. Once your graphics are awesome, make a movie (Final Fantasy).