Would be great for a general tutorial on how to get started for many people. Personally, I run into frequent issues with VNs where the lewd scenes are too easily obtainable or just downright unbelievable. Balancing plot and remembering to keep the game tastefully lewd must have a golden ratio somewhere.
I had this issue when I first started making my game, I didn't knew how to implement story branches without doing hundreds of extra renders or a bunch of extra text that nobody would read because it will be in the "bad ending" path, I have learned a lot now almost 2 years after I started it, I now have the knowledge of how to implement them but redoing the eraly stages of the game and story would be too much, I will instead implement it in a future game.
About balance and plot, if your game has a lot of dialog people might get bored, the same applies if it's endless sex without meaningful dialog, I believe a good balance is to have around three small conversations or one big ass conversation before a sex scene, and be sure to show something sexy in them or in between conversations, like a nip slip, upskirt shots, or just make the characters super lewd with skimpy clothes so players can focus on the sexy characters while they are reading, a handjob or some tit play during the dailog helps too, players get bored very easily.
I personally drop any game where I have like 10 minutes of dialog without anything sexy on it, just the main character and some love interest fully clothed talking for minutes isn't for me.
A good way to keep your lewd scenes reachable but not easily obtainable is to implement what a lot of devs do, a point system, you usually see it with corruption or love meters, but this can also become annoying if you need to farm too much to get that sexy scene and become easily repetitive, I will implement a conditional system in my next game, what's a conditional system you ask? see example below:
Player is in a situation where he can have a sex scene with character "Jane"
Player has two or more choices A,B,C,etc
Player can only choose one, lets say, A is blowjob, B is fingering Jane, and so on.
Player chose A, scene goes and ends, player has now a history of a blowjob with Jane, but no fingering history.
Player bumps into Jane again at a later stage in game is able to have a sexy time again.
Player has a few choices A2, B, C,etc
Where A2 is an even hardcore blowjob than before, B is the same fingering scene that was available before, etc.
Player will keep doing that until the full sex scene becomes available.
The downside of that system is that you have to keep the love interest in the same environment unless you do multiple scene with the same content on different backgrounds/environments, could be useful in a gem with a neighborhood where every character stays at home, school, etc.
In my case I have the idea to keep characters on two places only, their quarters and their working deck, it will be in a spaceship so everyone must be either working at a specific location on the ship or resting on their quarters.