Tools/materials pens, paper, ancient and modern calligraphy stickers
0 1 according to my personal experience in practicing calligraphy, it is ok to learn hard pen calligraphy without a teacher, but learning brush calligraphy is different. It is best to have a teacher to guide you, so that you can make faster progress.
If you just entertain yourself, hard pen calligraphy can be taught by yourself. Now the internet is so developed, you can find some celebrity copybooks or some calligraphy videos online, and then it is not difficult to write a good hand through hard practice.
If you don't entertain yourself and want to improve and achieve something in calligraphy, the best way is to ask the teacher for guidance. Calligraphy is extensive and profound, and it is difficult to improve it greatly simply by self-study.
Personally, I don't advocate self-study. It's better to have a teacher's guidance, so that we can not only avoid detours, but also help us lay a good foundation and make learning easier.
With the guidance of a good teacher, you can often get twice the result with half the effort, and it is difficult to practice good brush calligraphy simply by self-study. Good brushwork is impossible without long-term practice.
Teachers can guide you according to your personal situation and find out your shortcomings. Maybe a little guidance can save you a lot of trouble.