One Thing That Confuses Me About “Marxism” As An Ideology

Is how Marx’s own ideas varied over the course of his lifetime.  He changed.  He developed.  

So like which Marx?

(I like Marx a lot and sometimes even call myself a Marxist/Marxian so this isn’t like some anti-Marxist thing, just like curiosity over how people deal with that?  I guess like I tend to find he developed in understanding as he got older and like his later stuff best)