There is no fixed minimum, but the reality is that very small budgets make it harder to gather useful data quickly. If your industry has high cost per click, a 5-dollar daily budget might only get you one or two clicks a day, which is not enough to learn anything meaningful. A good starting point is a budget that can get at least 50 to 100 clicks a week so you can see patterns and make real decisions. What budget range do you think is realistic for a beginner running their first campaign?