There are many good calligraphers, including Mr Pang Zhonghua, Mr Tian Yingzhang and Mr Lu Zhongnan. They have published many running scripts and copybooks, and personally prefer Mr. Wang Zhengliang's hard-pen calligraphy.
I suggest you choose a style you like to practice, which will be more handy.
Don't be eager for quick success and instant benefit when practicing calligraphy. If regular script has a certain foundation, you can practice a few lines of regular script every day according to your own ability until you are familiar with it. In the process of practice, you can find some words that can be written into the work to practice. After practicing for a period of time, you can write the practiced words into works, which can increase your self-confidence and find out the shortcomings through your works.
If there is no basis for regular script, it is suggested to practice regular script at the same time, regular script practice seven and regular script practice three.
There are many good copybooks recommended by China's calligraphy, such as Tang Huairen's Preface to the Collection of Characters and Zhao Mengfu's Thousand Characters. You still have to choose according to your personal preference, but you must remember to choose copybooks with many words.