Probably not a lot can be "tuned" on the Wordpress side of things. However, you can tune the database behind it. If the database is slow the whole site will appear to be slow. So tuning MySQL is probably the first step.
Don't just blindly use an "optimized" my.cnf you found on the internet for MySQL. What is optimal for my sites and database usage may be completely unworkable for your situation. Let the database run for a couple of days then run databases/mysqltuner to see what could be optimized. Setting various caches correctly for example can really improve the site's responsiveness.