My own introductory textbook is Korean, the exchange standard between China and South Korea. Just as learning English begins with reading and writing letters, learning Korean begins with reading and writing Korean letters. Each chapter in the book consists of text, new words, common words, grammar and exercises. You can take the exam while studying. It is quite recommended to use multiple books.
Personally, I suggest that you don't have to buy a lot of textbooks at first, just choose a practical one, because after all, it is an introduction, and if it is too complicated, it will easily lose interest.
It took five months from zero foundation to self-taught Korean Level 2, mainly relying on learning textbooks, memorizing words, writing and brushing questions. After five months of winter vacation, I know I am lazy, so I will try not to stay at home during the winter vacation, but go out and find a place to study.
Many people say Korean is too simple to enter the exam, but I think it is necessary for self-taught friends to enter the exam. First of all, this is an official and fair opportunity to test your academic performance. You can take this opportunity to familiarize yourself with the examination room, experience the examination atmosphere, and then take the intermediate examination. Secondly, passing the primary exam can greatly enhance your self-confidence. After gaining self-affirmation, you will have more enthusiasm and motivation for learning. To tell the truth, everyone will slack off. When you want to give up, you certainly need a successful exam to encourage yourself.