How much disk space do you need to install Joomla!?
From Joomla! Documentation
Depending on the version of Joomla! that people install, a typical default installation will require between 40-50 Megabytes (Mb) of disk space without additional extensions or media (such as image, audio, or video files). The database will be small when at the start (less than 0.5 Mb) that grows when adding more users and content and additional extensions).
Be aware that some unofficial installation packages exists—such as those offered by webhosting providers or third-party extension vendors (e.g. installations for demonstration purposes)—that contain extra features not available with the official installation package. People who use these unofficial installation packages should also be aware that the Joomla! project does not recommend or endorse these things and they often result in leaving websites created by these unofficial methods vulnerable, unmaintainable or unsuitable for long-term production use.
The Joomla! project recommends people should download the latest version of the installation package (available from https://downloads.joomla.org) and that people should regularly update/upgrade their website to the current stable and supported version. A quick summary of the technical requirements needed for operating the Joomla! CMS can be found on the Joomla download page.