How many ETFs should I own as a beginner?

As a newcomer to the investment world, I'm wondering about the quantity of Exchange-Traded Funds (ETFs) that I should hold in my portfolio. Is there a general rule or recommendation for beginners like me? Should I start with just a few and gradually add more as I gain experience? Or is it advisable to diversify right away with a broader range of ETFs? I'm looking for guidance on balancing risk and reward while starting out in ETF investing.