The reason you chose to study a subject to educate yourself in depends on why you are interested in that particular subject. That dictates how you approach the learning.
If it is to further your career, you can follow formal courses to gain qualifications. If it is something which has caught your imagination, you have a freedom you don’t have with formal study.
Formal courses need to be researched carefully for accreditation and the value of their teaching in the market place. The material they offer also has to be relevant. Does it deliver the information you need to make progress? Is it distance learning only or can you have access to tutors. While distance learning is well organized and efficient now, contact with a tutor can give that little bit extra. The questions which arise that a discussion can solve is beneficial. A difficulty with formal courses is they have an exam based concept which needs specific material to be covered to be able to answer the questions; whether in an exam or as continuous course work. Often there is little time or energy to explore deviations from the laid down text. Because the subject is a necessity it is sometimes difficult to summon up deeper interest; and some subjects are very dry.
When the subject is something you want to follow because you are curious about it, you have to freedom to follow tangents and explore aspects which tend to be sidelined with more formal work. For instance, if you are tracing the history of the town where you live, a short paragraph in a local newspaper can catch your eye with a comment about an inhabitant. Why were they mentioned in that context? Then you have a train of information to follow. You can end up being far better informed by following an interest because you get involved with the material and end up digging far deeper into the subject.
You can also link your interest subject with a formal course which will give qualifications. That will give you the official viewpoint. But because the subject is for interest, you have more time and less pressure to widen your knowledge.
It’s possible to educate yourself in a surprising amount of subjects without formal courses. Factual ones can be a matter of rote learning and gathering the information, but subjects like history are open to interpretation about causes and effects. Finding differing points of view can produce surprising results and send you down other paths which at first glance are not related. While keeping your eyes and brain aware of what you are finding out, you can also chose to ignore material which does not interest you. The danger here is that you might be missing an important ingredient.
Educating yourself in any subject can be a bit like a detective story. You find clues and follow them, confirm them and gradually build up a picture. Like any learning, it should be fun, somehow you take it in better that way.