You think a group would be bad to learn from?
Groups are not automatically bad. You might have trouble finding one to accept you just now because of your age, but many groves have courses online for free, at least the beginner courses.
If by ranks you mean Bards, Ovates, and Druids, those are not hierarchical ranks so much as different branches of study. I'm not sure of the exact differences, since druidry isn't my path, but there is a lot of structure out there if that is what you are looking for.
You won't be able to take their courses, but if you want an overview and a lot of discussions to read, you might check into the OBOD website. There are others, too - I just can't call their names to mind at present.
Absent