One group adheres to a doctrine that being a believer is just rudimentary. Paul told Timothy to "show yourself an example of those who believe" (1Ti 4:12 NASB) who are "believers" (KJV). Being an example should be convincing and persuasive. Abraham was "fully assured [of] what God had promised" (Ro 4:21). Jesus told them to "'be not faithless, but believing'" (Jn 20:27 KJV) and "do not be unbelieving" (NASB). The concordance translates "believers" from the Greek word pistos meaning "trusting in a sure and true way." It is from the Greek word peithe meaning you have "confidence from an inner certainty." Believers "added to the Lord" (Acts 5:12 KJV) were "believers in the Lord" (NASB). With the Greek word pisteuo they have faith in something by entrusting and committing themselves beyond their own limitations to God. In terms of the Greek word pistis, they place their reliance and assurance on God's fidelity. This is beyond being just rudimentary.
The groups that promulgate a rudimentary believer is in a precarious position and must undertake discipleship in order to survive, argue that to "'make disciples of all nations'" (Mt 28:20) means to sign them up in a program to do that. They observe that "by this time you ought to be teachers" (Heb 5:12) and some endeavor to become official mentors to accomplish this. But to go to "'all the world . . . to all creation'" (Mk 16:15) to "'make disciples of all nations'" (Mt 28:20) does not mean that each person must get a degree in theology. We are to "teach" (:20), "preach" (Mk 16:15) and "proclaim" (Lk 24:47). But "the anointing which you received from Him abides in you, and you have no need for anyone to teach you" (1Jn 2:27). "You have an anointing from the Holy One" (:20). By "beholding . . . the glory of the Lord, [you] are being transformed into the same image from glory to glory, just as from the Lord, the Spirit" (2Co 3:18).