I would say that depends on you. Some people learn better through courses, other people learn better through self-education. And probably a combination of both is best.
Right now I started studying celestial navigation myself, bought some books and just studying them, when I don't understand something I just google it. Looking now for a sextant as well, and nowadays it would be so easy to test yourself considering all the electronics you have available as well.
All in all, I would say its always best to start studying yourself and then if you feel it doesn't go well look for some courses as well. Its always better to go for the courses anyhow a little bit prepared.
Right now I started studying celestial navigation myself, bought some books and just studying them, when I don't understand something I just google it. Looking now for a sextant as well, and nowadays it would be so easy to test yourself considering all the electronics you have available as well.
All in all, I would say its always best to start studying yourself and then if you feel it doesn't go well look for some courses as well. Its always better to go for the courses anyhow a little bit prepared.