All scripture is given by inspiration of God and is profitable for doctrine, for reproof, for correction, for instruction in righteousness: that the man of God may be perfect, throughly furnished unto all good works. (2 Tim 3:16)
Study to shew thyself approved unto God, a workman that needeth not to be ashamed, rightly dividing the word of truth. (2 Tim 2:15)
To start with you need the word of truth: the Authorized (King James) Version.
Secondly, you must study all of it to fully understand God and His will.
Thirdly, you must rightly divide it to obtain correct doctrine for the church.
The Bible is a book of progressive revelations.
What is revealed to one person or group at any time does not necessarily apply to another person or group at another time.
It is important to know the order in which the books are written and to whom they are written.
Most of the Bible is written to and about the children of Israel, or the house of Israel.
Only a few books are written about and to the church which is His body.
God’s dealings with Israel are examples for the church to learn from.
Some things that are omitted speak as loudly as what is written.
Paul is the chosen apostle to the Gentiles and to the church, which is His body.
Seven of Paul’s epistles were written before the mystery of the church was revealed: 1 & 2 Thessalonians, 1 & 2 Corinthians, Romans, Galatians, and Hebrews
Seven of Paul’s epistles were written after the mystery of the church was revealed: Ephesians, Philippians, Colossians, Titus, Philemon, 1 & 2 Timothy
Matthew, Mark, and Luke were written during the Acts period to Israel.
James, Jude, 1 & 2 Peter, 1, 2 & 3 John were written to Israel during the Acts period.
John wrote the book of Revelation near the end of the first century to Israel.
John wrote his gospel at the end of the first century to all men alike.