can we put Site, sub-site and User level quota in SharePoint Online !
As far i know, you can set the Quota only for the Site collection not subsite level in SharePoint.
Read more about the set storage quota check this.Manage site collection storage limits
Another thing, for indivual User if they are using the One drive for bussiness then you can set the quota on it for specific user. You can increase it upto 1TB.