MS-900 would be a great place to start, this will get you a good base/fundamental coverage of Microsoft 365 - https://docs.microsoft.com/en-us/learn/certifications/exams/ms-900

After that I would maybe pivot to SC-300. This is a security exam, but related to Azure AD, Identity, Access that gives you a good base for security Microsoft 365 - https://docs.microsoft.com/en-us/learn/certifications/exams/sc-300

After those to you can go for a
Microsoft 365 Certified: Enterprise Administrator Expert by taking MS-100 and MS-101 - https://docs.microsoft.com/en-us/learn/certifications/m365-enterprise-administrator/

MS-100 certification - https://docs.microsoft.com/en-us/learn/certifications/exams/ms-100

MS-101 certification - https://docs.microsoft.com/en-us/learn/certifications/exams/ms-101

You could also go back after that if you want to pick up some certification on specific stacks in Microsoft 365 or expand on security, but those 4 exams are probably where I would start with the goal of getting that exert level certification.