Start with the New Testament, and read a Gospel first. That is the most common advice you will get, and there is a real reason behind it. But it is not the only reasonable way in, and if you are drawn to the Old Testament instead, that is not a wrong move. Here are both cases, plainly, so you can pick with your eyes open.
The case for the New Testament first
The reasoning is simple: the New Testament centers on Jesus, and for a Christian reader, everything else in the Bible is understood in light of him. Starting with a Gospel, John or Mark are the usual picks, means you meet the main character before you read the story that leads up to him. It also front-loads the parts of the Bible that read most like a book you already know how to read: narrative about a person’s life, not law codes or genealogies. That is why most beginner guides and church reading lists point here first. It is the part most likely to keep you reading past week one, because it answers the question a new reader actually has, which is usually “who is this about,” before it asks you to sit with centuries of history that lead up to the answer.
The honest case for the Old Testament
The Old Testament is not a prerequisite you can skip, and there is a real argument for starting there instead. It is the story the New Testament assumes you already know. When a Gospel writer says Jesus fulfilled what the prophets promised, that line means more if you have already read the prophets, or at least Genesis and Exodus, first. Some readers also find they connect more naturally with the Old Testament’s poetry and narrative, the Psalms, the story of Joseph, the drama of the exodus, than with the letters that make up a large part of the New Testament. Jewish tradition, of course, reads these same books as complete scripture on their own, not as a setup for something else, which is worth remembering before treating the Old Testament as merely a warm-up act. If you are the kind of reader who wants the setup before the payoff, starting in Genesis and working forward is a legitimate way to read the Bible, not a mistake to be corrected.
What most reading plans actually do
It is worth knowing that the two common formats disagree with each other. A standard “Bible in a year” plan usually runs straight through in canonical order, Genesis to Revelation, so the Old Testament comes first simply because it comes first on the page. A beginner’s guide or a devotional, on the other hand, will almost always recommend a Gospel as the very first thing you read, then loop back to the Old Testament once the center of the story is familiar. Neither format is wrong. They are built for different readers: one for someone who wants structure and completeness, the other for someone who wants to be hooked quickly. Knowing which kind of reader you are is more useful than knowing which plan is more popular. A third format reorders Scripture by when events likely happened; see what a chronological plan does.
Where this is genuinely just preference
Neither order is required, and neither is more spiritual than the other. Christians have read the Bible both ways for centuries. What matters more than which testament you start in is that you keep reading and that you read the whole book you started, not a few chapters. Someone who thrives on plot and character might do better starting in a Gospel or in Genesis. Someone who wants context before commitment might prefer to read a short overview of how the two testaments fit together before choosing either one. There is no wrong answer here, only the one that gets you to open the book again tomorrow.
If you are still not sure
Pick a short, complete unit and finish it before deciding what is next. From the New Testament, that means one Gospel, cover to cover. From the Old Testament, that usually means Genesis, or a handful of Psalms if you want something you can read a few verses at a time. Finishing one book will tell you more about which half of the Bible suits you than any amount of deciding in advance. For a longer list of solid starting points on either side, see the best Bible books for beginners. And if choosing day to day is not for you, a reading plan will make the order decision once and let you just read.
Most people are better served starting in the New Testament, and if you have no strong pull either way, that is the safer default. But if you are the kind of person who cannot stand starting a story in the middle, start in Genesis. Either way, the Bible was written to be read the whole way, not just its first half.