Gonzales allows to conditionally load CSS, JS and even plugins depending on page you visit. It's simple and lightweight tool thanks which you'll be able to get rid of useless CSS and JS files registered by themes and plugins.
ust be clear, this WordPress plugin do not remove files from server - it's safe speeding up tool. If you accidentally break website appearance you can disable plugin and website will present old, unoptimized version. Btw: it's good approach to compare before/after timings ?
HOW TO SPEED UP WORDPRESS?
I created separated article about common problems and you should definitely read it now. In big shortcut answer to this question is: by conditional resources (assets/plugins) loading. Goal is to:
minimize number of assets (CSS/JS) (faster rendering, reduced CPU/GPU usage on end device)
decrease document loading time (minimized TTFB timings, reduced CPU & RAM usage on server)
You can read detailed Gonzales documentation explaining how to speed up WordPress in theory or take a look at App Shah's review to understand how it works in real life (Crunchify website case, v.2.0.x used):