I work alone, I'm still learning. I don't have much expertise, but a lot of time. I usually start with a very rough story idea (I make RPGs), then I create the maps, the ambience, and add music and sound effects. Out of the maps then comes the detailed story and the dialogues. Then I go back and develop the main thread of the story further. It's sort of a cycle, until the game is complete, but it always starts with the maps. For "Benji's Tale" (release on itch.io January '18) I used the "Journey of the hero" as a narrative structure. For "Moonstone Deep" (https://criacuervos.itch.io/moonstone-deep) the story was mostly inspired by the maps I created. Unconventional, but it works for me.