To stop receiving marketing email filter by the word "unsubscribe":

In Gmail, simply click on the gear symbol in the top right, choose "settings" from the drop down menu. On the next page select "filters". At the bottom, select "create new filter".

On the next screen, type in unsubscribe in the "Has the words" field:

Then select the following settings to remove them from your inbox. 

Pay special attention to the "Apply the label" field. You might want to create a label there called "Marketing". That way, if you ever find you have important messages missing from "trusted organizations" you can update the filter by clicking on it and adding the name of the organization in the "Doesn't have" field on the first screen.

To learn more about filtering out emails, check out this help guide by Gmail.