First, how about some more information from you? What are some of your hobbies? What do you like to do outside the home? Do you have a college degree in anything? Are you certified in anything? Do you have at least 10 years experience on a certain topic where you have worked in that field? Have you had any life changing experiences where you gained knowledge of something? This could include cancer, HIV, taking care of a disabled adult or child,,,,,,,. The best "niches" to pick - especially for the long term - are ones that you have personal knowledge about. The best places to start are your education, work experience or personal long term knowledge of a topic.
First off what you say may not be a good idea. You never know until you set the wheels in motion. Next best thing I would do check the keyword tool here at D P find something and research it study it like you are doing a test to pass to go in the next grade to get high scores. Then set that in motion.
ok, choose your favourite game and maybe do a blog about your progress throughout the game - similar to a walkthrough. People search for those all of the time - when they get stuck in a game.
i suggest asking a problem question in Google ad word that starts with how to! Like how to leash train dig