My suggestion is to lay a solid foundation for regular script before learning. It is impossible to understand the structure of words by copying copybooks, so it is very important to understand regular script thoroughly first! I am also learning pen calligraphy. If I have a teacher to teach me, I recommend you to practice regular script: Wen Zhiming's fallen petal poem.
Beautiful font, with charm!
If you want to buy copybooks, most bookstores have them, but the writing methods of running scripts are also various, so you should choose carefully!
Satisfied, please adopt!
Falling petal poem: