Start with philosophy, particularly epistemology and logic. You don't have to go too far indepth, just try your hardest to gain something from what you read.
Without letting it get to your head, take classical thought experiments (Ship of Thalassus, Hempel's raven, etc.) and think about them on your own without any guidance, and what they might mean to you. How the problems of identity, or the problems involved in ascribing essence to any object might work throughout your day-to-day. Once you think you've incorporated it into some kind of working model with what you already know, only then you should seek out the thoughts of others.
Soon enough, over time, you should have a good grasp on what it means to know things on a personal level- to ascribe identities, values, and even to differentiate objects. This is the cornerstone of knowledge, and is imperative to have some understanding of it in order to fully grasp anything else. There is no one understanding- that's okay though, it's just such that a coherent model can be formed for yourself that the utility is important.
From there, look at things on a systems approach. Knowledge you have =! Scientific knowledge and vice versa. Scientific knowledge exists within a system with which truths are referential only to it- similarly, mathematics, logic, history, language, etc. are all self contained systems for which there might be rights and wrongs within them, yet again there will be no 'objective' to be found anywhere.
Learning how a system works as a mechanistic macrocosm for the individual is incredibly important as well, as it will often give rise to knowing how such systems are born, how they propagate, and ultimately why knowledge within the systems are important, which will then allow assimilation of information to occur without dissonance.
For any formalism, again, epistemology and logic is your best bet.
