GIT - How to allow my customers to view different branches of a website

we use GIT as our source control and I was wondering what the best way was to allow my clients to view each feature branch (as the website itself) for review and approval of the new feature. (we could have several different features in development for the client at any one time - all going live at different times)

Currently we have to create separate test sites for each branch. E.g.:

Master branch (live): www.lovelywebsite.com
dev branch: lovelywebsite-dev.mytestsite.com
new-homepage branch: lovelywebsite-new-homepage.mytestsite.com
new-feature1 branch: lovelywebsite-new-feature1.mytestsite.com

This method takes quite a bit of time to setup a new test site (inc db etc) each time we create a new branch. It also eats up our server resources. (some sites can be many GBs in size)

We need to be able to allow the client to view these features and approve them before we can merge into master and push live.

How do other people achieve this? Any hints and tips welcome!

Thanks