There are quite a few ways on how to optimize your site. Here are a few steps you can take to increase your sites performance (most of them have plugins:
Cache your site: use cache tools like WP Super Cache. Cache will ensure your site will be held in memory as a static page, this means your server doesn’t have to re-process everything.
Minify and Combine CSS and Javascript: You can use plugins like: Autoptimize and Above the Fold Optimization to minify, async, compress or defer the loading process of resources like CSS and JS. keep in mind that this can mess up your site! so try all settings to see what works best for you
Enable server side compression: If you have a good hosting, you can go a bit more technical and optimize your server settings to help you with performance.
All these tools are freely available, and are, with some time invested pretty easy to handle.