As stated in the documentation
While you can serve your content through HTTPS using direct URIs such
as https://storage.googleapis.com/my-bucket/my-object, when hosting a
static website using a CNAME redirect, Cloud Storage only supports
HTTP
As you correctly stated using the loadbalancer is a recommended method to serve your content trough HTTPS. If you need help with this I would recommend you to ask another question with the details of the steps followed and the error impeding you to continue.
Using a load balancer will let you use Stackdriver to monitor the access to your account. Using Stackdriver you can get custom metrics and get the number of users entering your website.
Also discussing your Google Cloud Platform billing invoice in Stackoverflow is not recommended as it is not related to programming. If you need help with your billing you should contact the Billing support team of Google Cloud Platform.