Is it prudent to go to college? For example, I’m interested in studying the philosophy of personal decision-making which is a subject matter that very few philosophers study and write about. I don’t think I could find a single good course on this topic in any university. It’s actually even hard to find a lot of helpful material online about this topic. I usually try to focus on studying psychology, personal finance, persuasion skills, value theory, and do research on various important life decisions. Unfortunately, these are just not things they teach you in school. — TheHedoMinimalist
Whether you pursue education within an institution or pursue it outside of the same, it is mostly a practical matter. Do you need a recognized degree? Can you afford college? Will you be admitted? Do you have the personal characteristics required to do well in college (and at the same time, do well outside of college)?
If you do not need what a college offers, and you can get what you want and or need elsewhere, then fine. But I don't know what your situation is; how old you are, how knowledgeable you are, what your history and long-range plans are.
Researchers do study personal decision making, from various angles. Take risk, for example. Whether you are risk averse or risk tolerant will affect the kind of decisions you will make, and to some extent, how you will make them. Risk averse people are likely to be cautious about how they make decisions (gathering safe, reliable information for example) as well as which decisions they make. Risk tolerant people may also gather reliable information, but treat it different than a risk averse person. People are not always consistent from thing to think. An individual may be risk averse about money, but be risk tolerant when it comes to sex.
I think you are probably correct that no single field of research (wherever it is done--on campus or off campus) treats "personal decision making" as its territory. Too bad, because that is where most of us make our worst mistakes.
One of the most important personal decisions is, "What do I want to accomplish in life?" I have sometimes asked college students to think about the next 5, 10, or 15 years. What do I want my life to be like in 10 years? What kind of home will I live in? Do I picture myself being married, partnered, single, with children, no children, how employed? How much money (in today's dollars) do I think I will need to live, and so on. Paint as detailed picture of your planned future as you can, then working backward from the future, "What do I have to do to make that possible?"