getting error when trying to set the org, its taking my machine name and throwing error, can someone help please (am using gcp bucket as my backend state storage)

The oss backends don't support organisations

How can create an organization then?

you don't need to create organizations to use gcp buckets(iirc)

You cannot create an organisation in the oss backends

But if i setup self hosted pulumi service then i can setup org right?

yes, but the self hosted pulumi service will require a conversation with an Account Executive