All anyone needs is the Holy Spirit. No multiple languages, and no theological study will ever save a soul, but Jesusw Christ's sacrifice for us all.
As for what to study, if so inclined, to my great glee I discovered all I really need learn is Jesus Christ, and that is a lot. Hearing His teaching, that is studying guided bty the Holy Spirit, one will learn much , and we learn directly from God.
He says it, His burden is light, and His yoke is easy........learn of Him.......... What an holy invitation. For me it is irresistable. I pray it is the same for all, amen.