I would suggest that as an aid to learning that you pick a topic where you have some familiarity or experience.
Then you might search this forum or even a general google for things related to that topic to find the types of things people ask about.
The familiarity with a topic will help you when something odd appears in results. Which either brings up more interesting questions to evaluate or a clue that what you may have attempted in an analysis was not quite correct.
"Know thy data" is important. So I would suggest starting with the tools to examine data of interest for accuracy or completeness, i.e. descriptive statistics.