Answer: Before we arrive at which modern translation is the most accurate we need to know a little bit about the manuscripts (writings) translators have used to produce copies of the Bible such as the King James Version and others.
The manuscripts commonly used for the translation of the Old Testament into English are the Masoretic Text (MT) and the Septuagint. The Masoretic text is the textual tradition and marginal notes of the Levitical scholars known as Masoretes. Active from about 500 to 950 A.D., they continued the work of earlier Aaronic priests and Levitical scribes who were appointed by Ezra the prophet to be the official guardians of the Hebrew text he helped canonize.
The MT is considered by many to be the authoritative Hebrew text of what we today call in the Bible the Old Testament.
The Septuagint, which means "seventy," is a set of Greek manuscripts of the Hebrew-based Old Testament. Also called the LXX (the Roman numeral for 70), the text is believed to be the work of seventy Jewish scholars that assembled in Alexandria, Egypt around 285 to 247 B.C. The most common manuscript families used to translate the New Testament into English are called Byzantine and Alexandrian (Egyptian).
The Byzantine family, also known as the Traditional or Majority Text, was the text used and preserved by the Greek Church from the time of the apostles until the era of movable type printing. It is from this family that the manuscripts known as the Textus Receptus (also known as the Received or Stephens Text) were produced. The Textus Receptus was the translation base for the original German Luther Bible, the New Testament into English by William Tyndale, the KJV and others.
The Alexandrian Text manuscript family is composed of texts that were generally circulated in the region of Alexandria. This family essentially disappeared for centuries after 500 AD, only to be found again in the mid-1800s. Although these manuscripts are quite old, they often disagree with one another and show significant signs of grammatical revision. It is from this family that the Sinaiticus and Vaticanus manuscripts are produced.
The best translation
Now to your question about what is the best English Bible to use for your primary studies. I would suggest one that uses the Masoretic text for its Old Testament translation base and the tried and true Textus Receptus (Received Text) manuscripts as the basis for its New Testament. Scriptures based on these manuscripts include the New King James Version and the Holy Bible in Its Original Order.
I had been using the New American Standard but when we understood more about the manuscripts, we went back to using the KJV version. I do not know where you are in your walk with God but as a new learner who needs to understand the concepts in a basic way I suggest buying a good paraphrase version of God's word such as Good News Bible.
If you are a more mature Christian and you prefer to compare texts then do so, but just remember translators take a lot of license as some idiomatic and figurative phrases do not readily translate out into the English language well.
Many of the newer versions have stopped using the Received Text for their New Testaments and are instead using the Vaticanus manuscripts with their many errors.
It pays to be careful in selecting a new copy of God's word. Not only are ministers preaching unscriptural doctrines the very Scriptures themselves are being corrupted as well. We must be very aware of these facts in order to discern God's truth from lies. Thank you for submitting your question about what is the most accurate Bible translation.