First off what is website hosting?
Its where you are allocated space on a computer storage drive at a data center where you securely keep your website files for public or private access.
And a data center is a building with a fleet of interconnected computers just like your home computer the only difference is that the data center computers are always online 24/7, highly maintained and optimized for higher performance.
The direct answer to how much space you need is, it depends on your current file size and expected growth.
Hosting companies or resellers have numerous space options depending on your needs and definitely your pocket.
Based on my hosting experience, if you are just getting online I would not advise going to something lower than 10gb of hosting space.
This space is sufficient to host your website files, accommodate future changes and host your emails.
Most hosts come with an option to upgrade/Downgrade your space. Therefore if you outgrow the current space you can upgrade accordingly.
I know most host claim to offer unlimited space but this is a marketing gamic.
Unlimited simply means you are free to use the server space subject to the host storage limit.
For instance, if I am a host with 200GB hosting space when I give you unlimited storage space its limited my storage space of 200GB.
So nothing is unlimited.
I don’t know about you but I would be happy to know how much space I have on a server to plan accordingly.
A real-time scenario,
We have a heavy usage client who for the past 5 years has used 20% of his server space(Starter package 50Gb), going by his usage data this server space will be sufficient for the next 25 years after which he can upgrade his package.
If you are totally clueless on what space you need, look for a good host and signup for a basic package.
As your business grows you can upgrade the server space accordingly.