There are a number of ways to accomplish what you want. Experiment to see what works best with your team.
We use recurring tasks to manage these (we had one board with lists for Daily, Weekly, Monthly and Annual/Once tasks)
Method One: Each person assigned to a card will be subscribed to the card activity and therefore receive an email notice of activity when each person steps through their items (checks the list item box inside the card). Each person will learn what list entry completion entry means something they need to start next.
Example: Paul knows to start step two (list item 'Tweak the Ad') when Julie completes step 1. Julie could also add an activity entry starting with "@paul Ready for you to start step 2" in the card activity. The "@paul" code in the beginning of the activity notice generates a specific message to the user Paul.
Method Two: Create a separate board for "Ads/Adwords/Campaigns"
Then create lists for each task or person/team. Moving a card from list to list would move the task on to the next person/team.
List 1 might be "Ads waiting for approval" Each new Ad/Campaign would start here as a separate card waiting to be approved for the next action.
List 2 might be called "Marketing" where the marketing team tweaks the ads. Approved cards would be moved to this list. The most important ads (cards) would be at the top, least important at the bottom. The marketing team would have a list of their tasks here, in priority order.
The final list would be "Delivered Ads" (completed). This kind of board would give you an at a glance view of all open ads and, by list placement, show you what stage they are in.
In this way each List represents a person or team and the cards the list contains includes only the ads they are assigned to work on now.
Trello is very much a project management tool, it's just not a traditional "chain of due dates" PM tool. Once your team starts using it to get things done they will come up with even more ways to use it.