If you’re using WordPress, you’ll need about 50MB for the WordPress files, and then you’ll need space for plugins, themes, uploads, and backups.
Plugins should be about 10 – 30MB.
Themes should be about 2 – 20 MB
Uploads will vary depending on the type of website you’ll be building. If you’re selling photos, you might need 1024 MB. If you’re building a small business website, you should need about 5 MB for Uploads.
Backups depend on the type of software you’re using, but typically the database and wp-content are backed up, which would be about 2 – 10 MB for the database, and 20 – 100 MB for wp-content.
I’d recommend at least 500 MB website hosting space for a small business website. If you find you’re running out of space, your web host will allow you to upgrade your web hosting plan.