Has_many through and belongs to in Rails

I am working on a Rails app where a User can create a magazine and another user can subscribe to that magazine. I want to know the best way to do this.

Currently I have a subscription model that builds from current user when created and users the current magazine as the magazine_id. This allow me to have a table of user_ids and magazine_ids. This allows me to see all the subscriptions but it means I cant easily check all the magazines someone subscribes to or check all the subscribers of a magazine.

When I try to use has_many :through, it throws up an error with building from current user. I have put in the relevant code below, hopefully it covers it all and thanks in advance.

User model:

class User < ActiveRecord::Base
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable

  has_many :magazines
  has_many :subscriptions

end

Subscription model:

class Subscription < ActiveRecord::Base
    belongs_to :user
    belongs_to :magazine
end

Magazine model:

class Magazine < ActiveRecord::Base
    belongs_to :user

    has_many :subscrptions
    has_many :users
end

The snippet of code from the subscription controller that throws up the error when I use has many through

  def new
        @subscription = current_user.subscriptions.build

        @sub = Sub.find(params[:sub_id])

    end

Hopefully that is enough for someone to figure out, if not please ask me for the other code or information.