What do you advise me to do, and what books should I study to gain deeper understanding of religious matters, so that I can be a student of knowledge and a caller to Islam?

We ask Allah to keep you steadfast in truth, to complete His blessings and guidance upon you, and to grant you beneficial knowledge, making you one of those who invite others to Him. Indeed, your determination and resolve in seeking knowledge and engaging in Dawah are among the noblest of deeds. We have previously explained, in previous fatwas, the means of strengthening faith and steadfastness, advice for avoiding sins, the conditions of repentance, the etiquette of seeking knowledge, recommended books for beginners, and how one can be a Daiyah (caller to Islam).