I don't think there is anything in the game thus far that requires level 3 in any skill. There are a few cases where you need level 2 something, but level 3 usually is mastery in some skill and adds a strong bonus. Usually level 1 unlocks most of what you need.
As far as RNG. There is none. Points gained are for talking about things they like, and the xp gained is based on a few factors such as some certain skills you have, as well as how much they liked what you were talking about. You usually gain a new topic after talking about something 3 times. You can also gain topics by doing tasks that require no talking, like cleaning your rooms, watching TV, ect.
As stated before there is a 'beginner's luck' that usually kicks in after about 15xp that doubles all your skill gains until 100, and usually, things like watching porn can net you skills in multiple subjects, perversion one of them.
There are also online tutorials you can get at your computer that take a lot of time, but give you much larger XP gains (15?) for certain subjects, so if you need to waste time, go do those.
The main trick of the game is that if you focus on any ONE person or ONE skill it will seem grindy as fuck. Try to plan out the days better to gain a variety of skills each day: Porn for a few hours, Games for a few hours, Cleaning for a few hours, talking to Diane or Gina 1-2 times, research online, and sleep. Throw in an hour of watching TV or social media. Repeat the next day. Enough porn watching will unlock incest porn, which enough of that will allow you to peek on showers, do some things with Gina on nights where she comes how drunk.
