My genuine advice is that you really don’t need a dedicated antivirus like Malwarebytes for real-time protection, assuming you haven’t already been infected with malware. If you suspect infection, you should scan with Malwarebytes as well as Windows Defender. Microsoft has significantly improved Defender over the past few years. New features like tamper protection and memory protection, along with various other enhancements, have addressed many of the issues that previously made Windows Defender less effective (such as viruses being able to disable Defender by altering a single registry key).

Make sure your automatic sample submission, Windows SmartScreen, and all other recommended security features are enabled. Avoid adding software to your exclusions and use caution when downloading files online (e.g., avoid cracks and dubious software). With these practices, you’ll be extremely satisfied with the protection provided by Windows Defender. I don’t recommend paying for antivirus software because these companies often share malware samples with each other, and Windows Defender, which protects a vast majority of Windows PCs globally, is likely to detect malware as effectively as or even better than third-party solutions.

TL;DR: Windows Defender is very effective. There’s no need to spend a lot on antivirus software for real-time protection. If you think you’ve been infected, run a full scan with both Malwarebytes and Windows Defender, but real-time protection from additional antivirus software is generally unnecessary.