We OPTIMIZE PERFORMANCE on a lot of models for Power BI. And, over the years, we start with the same first few things. Adam walks you through his steps.

Performance Analyzer:
https://docs.microsoft.com/power-bi/create-reports/desktop-performance-analyzer

DAX Studio:
https://daxstudio.org/

Tabular Editor:
https://tabulareditor.com/

Best Practice Rules:
https://powerbi.microsoft.com/blog/best-practice-rules-to-improve-your-models-performance-and-design-v1-1/

Guidance Docs:
https://docs.microsoft.com/power-bi/guidance/

One Checkbox video: https://www.youtube.com/watch?v=RnDdDlozcdo