Everytime i enter "oxide.grant user BetaSpydog admin" it returns with "permission "admin" doesnt exist". Not sure what to do here considering that the defualt permission is admin.

There is no permission "admin", but there is group admin. Group dont have any plugins' permissions at start. But you can give all permissions to group admin using o.grant group admin * or user yourNameOrId. Also if you want to grant yourself a group, use o.usergroup add nameOrId admin

I would highly discourage blindly granting all permissions from plugins, that could be very bad and create a big mess. Players that are "admin"/owner in the games are also automatically added to the "admin" permissions group.