Your site has 200 visits per day, you don't need to take care about performance.
But if your site reach 2000 visits per day, the speed of your site matters.
Let's see tips from our team. We ues these tips for the busy traffic sites: http://wpml.org and http://wp-types.com.
This presentation was on air in Saigon on March 1, 2014 in the event: