Best Accessoires for Sony A7r IV

I recently bought my first Camera (i got a Sony A7r IV and a Tamron AF 28-75 mm f/2.8) and im looking forward to buy some more Equipment. I already got enough SD Cards. Im mostly shooting Clubs / Concerts and Fashion content.

Do you guys have any "Must Haves" for my new camera? From a flash to another Lens. Im looking forward to any suggestions.