There is no compulsory “correct” number
The number of cards in a tarot reading is primarily a methodological choice. My practical rule is to use one card for each question in a simple situation. For a complex situation, I use three cards and a significator for one question.
More cards do not automatically mean a more accurate reading. Sometimes a larger layout simply makes interpretation harder: each additional image attracts attention, and the original question gets lost.
What makes a situation complex?
I consider the number of people involved, how tangled their relationships are, and how emotionally charged the circumstances have become. A question about your mood today is relatively simple. A dispute among several relatives involving old grievances and financial interests deserves more careful examination.
Yet strong feelings do not always equal complexity. Someone may be deeply upset by a single brief message, but that alone does not mean dozens of cards are needed.
Choosing a layout without overloading it
Write down your question first. Then ask whether you need to examine several people and connections or whether one answer is enough. If one answer will do, start with a single card. If the situation is genuinely layered, consider a more complex approach, such as three cards plus a significator.
Ready-made spreads are useful when you do not want to design the structure yourself. Their positions are assigned in advance, but you can still omit irrelevant questions from your own reading session.
What matters is the meaning of the question and consistency in interpretation, not an elaborate arrangement of cards on the table.