Use google page speed test to check your page performance: https://developers.google.com/speed/pagespeed/insi...

It gives some suggestions on improving performance which you can follow.

Some common approaches:

• Concatenate and minify scripts and styles - there are lots of wordpress plugins for this
  This is also a moot point if you can upgrade your hosting to run http2
• Remove unneeded functionality, if using WordPress the key way to slow down your site is to add too many plugins without reviewing their affect on your site
• Upgrade your hosting - I've upgraded a couple sites recently to php7 which runs tons faster, especially after moving onto http2
• Optimise the images on your site, you can save a ton of space here - check out this service: https://imagify.io/

I would also add that you should only use enough to accomplish your goal.

What do I mean?

Not every website needs

• to be Wordpress.
• social media feeds
• tons of plugins
• more than 2 web fonts
• HD pictures or video
• user registration / login

Only build or use the functionality necessary to convey your message or run your business. Think about how things will load on mobile (which is much different than on a laptop or desktop computer).

If people don't want to use a lot of cellular data, you'll likely not get people to visit on their mobiles and/or tablets if just loading your home page chews through data.

This about the function of your website, your customers and their devices.

I wrote about speedup ecommece website in easy way here -

http://webdesignxperts.com.au/blog/speed-up-your-e-commerce-website/