Measure first
Run your key pages through PageSpeed Insights and note Largest Contentful Paint, Interaction to Next Paint and Cumulative Layout Shift.
Optimise images
Upload images at the size they are displayed, prefer WebP or AVIF, and keep WordPress’s native lazy loading on for images below the fold.
Cache pages
Use your host’s page cache or a caching plugin so most visitors receive pre-built HTML.
Audit plugins
Deactivate plugins you do not need. Each one can add scripts and database queries to every page.