How to set an action for ads in the application?

Question

Android

Good afternoon.
Tell me how best to track ads in the application.
I can't think of a better way to do it. It is possible to add only a limited number of goals to the task list, 10 items in the free version, upon reaching 10 tasks, I want to display a message about the subscription or viewing ads (most likely video) after the end of viewing, another 10 items will be available in the list for a week for additions.
That's where the question is, how to track when the action of the advertisement is over (7 days).
The first thing that came was to save the value in the database and check the date at startup.
And if there are several views of advertising in a week or a day, enter it with a new entry and so on by the number of views?
And then another question, what is better to use to display ads? Full screen banner, video?