This post is inspired by a 2013 post in the I Teach With Moodle blog.
The most useful advice is to avoid using Moodle as a server for multimedia, that is, video, audio and images. If you just have a few images saved into your Moodle course, there won’t be any problems, but audio and video files can be massive. It’s much better to store your multimedia files on external servers, such as YouTube (video) and SoundCloud (audio) . If you do so, your Moodle courses will be much smaller, which means that they will be easier to maintain (copy, restore, etc.).
Those of us that work with computer files (programs and large data sets) should also seek to store related files on external servers such as Google Drive, if this is permitted, in order to optimise Moodle.
http://www.iteachwithmoodle.com/2013/06/05/10-ways-to-reduce-the-size-of-a-moodle-course/