Measure first (PageSpeed Insights, or Query Monitor to see which plugins are slow), otherwise you'll fix the wrong thing. After that, in roughly the order it pays off:
1. a page cache. Your host's built-in one if it has it, otherwise one caching plugin. One, not two, they fight each other
2. images: resize to the size they're actually shown, convert to WebP, lazy load anything below the fold
3. get rid of plugins you don't need, especially sliders, page builders on pages that don't need them, and anything that loads scripts on every page
4. a lighter theme if yours is a big multipurpose one
5. keep PHP on a current version, it's a setting in most hosting panels
6. a CDN if your visitors are spread out geographically
If it's still slow after all that, it's usually the hosting.
