Hey,
A few weeks ago, I launched ResultRumble (https://www.resultrumble.com), a result prediction game centred on the Premier League.
Each week, users predict whether teams will win, lose, or draw, earning 3 points for each correct guess. There are about 10 games a week and the Premier League spans 38 weeks, so it's a long-term game.
I am giving £100 to the winner and £50 to second place. I did this to encourage people to play and it made me feel a bit better about posting it on Reddit and WhatsApp groups. It seemed to work as I acquired 349 users when my target was 50. Granted, I wanted 50 active users. I'd say about 200 are active (I'll be trimming the fat soon).
I'm not really sure if this will turn into a profitable side project. I was mainly doing it for the experience. It's my first full stack application built purely by me. For the devs, it's React front end, c# back end, mysql, hosted on VPS with Docker Swarm.
I will be improving it for next season and adding private leagues, so users can invite and compete against their friends in their own league, rather than being on one big leaderboard. Not sure if I'll offer prize money next season.
I've dropped the ball a little bit here, as I'm not actively promoting the site any more since 4 game weeks have already passed (I should have posted here during my 'launch'). You are still welcome to join in, but you will be on the back foot.