Or does each game just build on top of working knowledge of previous similar Games?
This. There is a sort of gaming DNA that you just internalize over time. I’ve been gaming for 30 years, I just know how that one breakable wall looks, that you need to come back to once you get bombs or whatever it is. I know the difference between a caster, a fighter and a rogue when I see them without knowing the exact details of their ability mechanics in this particular game. My intuition as to how a given ability is most likely going to work is also usually pretty close. Because they are often very similar across different games.
Also if you don’t know and don’t have to have the absolute optimal combination from square one, just pick what looks cool and try it. If it doesn’t work out, try something else. Most games allow respecs nowadays. We learn through failure and repitition.