Let’s see….
Matthew: A Levitical priest certainly obtained a superior education in OT Law and prophets, as evidenced by his continual use of “this was to fulfill the scripture (or prophet)
Mark: Not sure, but since he could write at all suggests some formal education
Luke: The beloved Physician: The only Gentile writer of scripture. Uses near Classical Greek in the first four verses of Luke and Acts. That, and that he was a physician suggests extensive education.
John (and James his brother) from a wealthy family. His writing style of frequent dualism and repeating themes suggest extensive education.
Apostle Paul: Clearly advanced education within Judaism as well as Greek culture and philosophies. This is evidenced by his mastery of OT Law and the use of the knowledge of Roman culture to appeal to his readers. Without question, Apostle Paul would have held a PHD by our standards.
Peter, Jude, James: probably little formal education.
So, the Apostles varied from having little formal education to extensive education. Those who wrote most of the New Testament had extensive education, certainly many years or even decades in Paul’s case and perhaps Luke as well.
The question is not “seminaries” but education. Spurgeon had no formal seminary education but had immersed himself in studying scripture and what others had taught about scripture for years prior to preaching.
I’d be very careful letting a new Christian teach after only 6 months, as teachers will be held to a higher standard by God for what they teach.
peace to you