I will tell you the core principle of self improvement. It is consciousness. It is awareness. It is your innate nature. It is discovering who you are.
Therefore the best you can enter this world of self improvement is being true to yourself moment to moment, with keen observation of everything in your experience. This keen observation, this state of being the awareness, being your true self, will transform the content of your mind as you maintain it.
All kinds of experiences will come your way based upon the direction and location already built into your mind through your past experiences. Treat everything as a learning experience while staying true to yourself. It doesn’t matter if you read a self help book, or eat an apple, or observe a farmer working in the field. Everything is a flow of information into your mind. When you are truly conscious while living your life, your experience of life will be enhanced, insights will come more quickly as you live your life more in the state of awareness.
Go buy a random self help book, something that appeals to you. But read it with awareness. Then life will proceed you to the next experience, you will have already grown from the previous experience.
Treat the concepts taught by others as concepts taught by others, see everything as it really is. If they direct you towards certain experiences, see them as they are. Be aware and as you experience life with awareness, you will see it as it is, and your understanding will increase, and you will have grown in wisdom.
Simple honesty while reading books, simple objective observation, and admitting you don’t know something will protect the freedom of your mind. If you accept concepts that you haven’t seen the truth for yourself as your truth, as such concepts pile up in your mind, your confusion will increase, because you have never truly understood what they mean, they will only be in your imagination if they are not based on actual understanding through awareness. So don’t just read, test them, practice and see if what they say is truth, otherwise treat them as untested ideas, be mindful of their untestedness.
If you proceed with these steps, intended to maintain integrity, you will be able to chart your own way in the vast information sea by preserving and increasing the integrity of your mind’s content, and sifting through already confused information that was already there before you started. Sooner or later you will be able to home in to universal truths discovered by great men, because great men reach them too by similar approaches. Self improvement is only real if it is focusing on truth, and what is the Self that you are trying to improve? It is one great question that spurs growth when one tries to answer it. (It did for me)
Examine the works of great men, but not by believing everything they say. If you want to grow to their level, you must match their diligence in science (seeing), and one can be diligent from the beginning levels if one really does their best. No concept, no teaching can save you if you yourself do not apply your power, apply yourself. Because concepts/teachings do not contain power, they were all created by those who had discovered their innate power. Your success depends on YOU, moment to moment, and no effort is ever wasted, all effort requires your power to create experiences and will increase your understanding one way or another.