I would first ask if you have a general theme or plot decided, then the feedback could be more specific.
Do me a favor and don't make a boring grind. See
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on this. It's a lot of reading, but you'll get the general idea pretty quick. The summary is don't waste the player's time. Everything in your game should either be erotic or move the story forward. You decide what kind of balance you want. If it doesn't serve one of those two things, then it should probably be optional.
Other than that, just good writing and believable characters. It doesn't have to be "realistic" exactly, but try to keep it somewhat grounded. Don't do this: "Nice to meet you, I'm Main Character, look at my huge dick." "Oh wow, what a big dick, I'd like to fuck you." Leave that for regular porn.