Setting your mc to be either boy or girl living with their family is popular. Girls usually virgins with high prude stats, and around 12 of age, boys a bit older and no regard for rule of law or societal norms. Having "18" y olds for patreon is an unfortunate trend, they're made retarded to compensate. f95 happily allows underage characters and people who mentally can't consent to have sex.
Gameplay where you explore areas, play minigames where you gain money or stats, do quests to open scenes are pretty mandatory or you're a visual novel. Combat in games is moving away from mindless grind to more difficult encounters that are sporadic or have plot relevance. Repetitive clicking action is normal in russian games but hated generally.
Stairway to heaven has you progressively increase the intensity of sex scenes. Girl starts off showing her body, handjob, bj, sex, anal, group sex, dog sex, dead sex, even rape. It's a popular formula for sure.
Agency is important at everything player does or sees, having a scene where you have no say in getting to it, or altering it has low value. It's better to have a goal, choices, and variation depending on how you progressed the game. Sometimes just different dialogue and facial expressions is enough.
Having well written characters to interact repeatedly over time adds value to the relationships as opposed to having numerous partners that are entirely irrelevant to the player and plot.
Writing and pacing are important in that some people don't want to read story that is there without a reason. If in doubt make sure each paragraph is relevant to the players motivations, sex, characters. Women have different priorities than men with the writing.
Setting with low effort games tends to be some modern american city because those kinda daz models are available easily. 2d games have easier time take place in medieval or 19th century EU since it's easier to accept people acting differently and you just draw the art and use readily available rpgm assets.
