Your diet for spiritual growth is God’s word. Spiritual growth is not an activity that happens at an instant, it is a lifelong process. A process that requires diligence and consistency. We understand that by believing the word we are saved ROM 10:8-10. The good thing here is that the preaching of these words. To the unsaved brings salvation to them and upon believing, this same word when taught to the saved brings forth growth.
After salvation, you have to see that you remain committed to the study of the word and giving to prayer personally and it is through your local assembly you will be equipped for this. spiritual growth is a function of what you are being fed with and has to be the word of God. What makes a believer grow is the knowledge of the word of God. Paul after his years in ministry still spoke about knowing God better Phi 3:10.
Spiritual growth is not a one-time thing. You do not outgrow it, as long as you breathe, you put yourself to deliberately growing in Christ. This growth happens via the word of God through knowing and praying. This is why prayer in the epistles was very loud about knowing. You know what you have and who you are in Christ. This is why praying and studying the word together and consistently is how you will grow spiritually.
Be concerned and deliberate about growing in the faith.