You could make a simple but useful app and bundle ads with it to gain profit from that and have an in-app purchase to remove ads for even more profit. Like for

You could make a simple but useful app and bundle ads with it to gain profit from that and have an in-app purchase to remove ads for even more profit. Like for example: You could make a calculator that appeals to people taking geometry like a Pythagorean Theorem calculator that shows the answer and work. Your best bet is to pick something easy that appeals to a group of people.