The one you will read. Maybe that seems like an oversimplification of a complex topic, but it doesn't matter if you have the most perfect translation ever if every verse feels like a chore to read and understand. Find a version that feels readable to you, get an audio version, a video version, have someone tell you the stories, whatever it takes to be able to personally get the stories so you can learn from them (and from now on, when I say read the Bible, this is what I mean.)
The best advice I ever got about reading literature in translation (and generally speaking we read the Bible in translation) was from the student assigned to show us around for Freshman orientation who took us on a brisk tour and then got us on a bus to the big used bookstore downtown and helped us shop for the many source texts required for graduation. He told us not to worry about getting the exact translations that the professors called for, but instead to look for a translation that we found readable and understandable so we would actually do the reading. He also pointed out that if we read different versions from others in our discussion sections, we might have different insights and that would give us something to talk about. This applies well to Bible versions. Translation is almost always a compromise between accuracy to the original text and readability in the target language and accuracy has a couple of different aspects, sometimes a translator has to choose between using words that best fit the the style of writing (particularly with things like poetry or a pun, but it could also be formal versus informal language) and words that best fit the meaning.
That said, the Italian proverb "Traduttori, traditori"
(Translators are traitors) applies to Bible translation as well. Even the most well meaning translators bring their own assumptions to the table. It is useful to be aware of those assumptions and most translations have notes, either in the published Bible, or online, where the translators explain their process and what they used as their base text. At this point, you are probably thinking, wait, a minute, isn't there just an original text, don't we just translate from the oldest version? Not always, and the King James Version in particular did not. And while that sounds bad, it can sometimes be justified - for example, at the time of Christ, many Jews and thus the early Christians used a Greek translation of the Hebrew Scriptures called LXX or the Septuagint for the 70 (or 72 depending on which history you believe) rabbis and scholars involved in the translation, so if we want to know how Jesus, the apostles and the early Christians saw these texts, we might want to start from that translation ourselves. However, Jews went back to using Hebrew scriptures and translating from them due to inconsistencies in the translation of the Septuagint, including the fact that some books were more retellings than translations. If you don't ever use the Septuagint for translation, you will miss some places in the New Testament where the Old Testament is quoted and possibly some important information about how Jesus, the Apostles and early Christians saw the scriptures. If you do use the Septegent, you will risk getting further from the original meaning by using a translation of a translation. Again, how this issue is handled is usually included in the translators notes. If your Bible version doesn't have translators notes and you can't find them on the internet, looking up the translation on Wikipedia often will provide at least some of the same information.
Why you are reading the Bible may also impact which version you use. You might want a different version for daily reading than for study. You might want a different version for reading the poetic parts like the Psalms.
Here are a couple notes on some English Bible versions and why you may or may not want to read that one:
New Revised Standard Version
This is the version used in a lot of seminaries as well as the basis for many study Bibles that are well regarded in academic circles. It is in modern English and reasonably readable, but it always chooses accuracy over readability.
Common English Bible
This is a very readable Bible and aims at a middle school reading level. My personal experience is that almost every word in it is in my active vocabulary - words that I would use every day and that that really causes me to focus on the text. It's a good version to use in worship situations because children and English language learners are likely to find it understandable. Despite using simpler language, it also usually gets good marks for accuracy.
The Brick Bible
This is more of a novelty Bible, but it does an excellent job of presenting the stories of the Bible in an accurate and engaging format. If you are a highly visual person, this is an excellent addition to your understanding.
The Message
A single author translation intended to focus on presenting the story in conversational English. It's great for reading (or listening too), the poetic parts are excellent, but it's probably not great as a study Bible.
King James Version - KJV (also known as the Authorized Version)
Some people believe this is the only version to use, don't listen to them or anyone who says to only use one translation. Because it was translated in 1611, it uses an older version of English that is harder to read and understand and I don't recommend it as a main reading and study Bible particularly for this reason. Some of the poetry in particular is translated in a beautiful and poetic way, so it can be worth reading, particularly in excerpt version. Because it is out of copyright, you can freely quote from it without worrying about copyright (although most translations have generous quoting policies), and it is sometimes used for this reason alone and KJV Bibles are cheap - the dollar store usually has a full shelf of them. (By the way, the reason copyright became a thing for Bible translations was not an effort to recoup the cost of translation, although that is an issue, but because people were writing in their own changes to prove their point and passing them off as original.)
