awesome-katas VS kaggle-environments

You can find lists that group exercises such as this one

This is true, by the way, for learning another language, as well. That's obviously a much higher investment, but it makes you more well-rounded as a developer. I regularly practice code katas, the same one in different languages and approaches, to constantly re-evaluate my way of thinking and solving problems.

If you are interested in Data Science, you may want to look at Kaggle competitions. https://www.kaggle.com/competitions

Secondly, if you feel like you do not have enough skills or a lack of practice answering problem statements, there are a lot of good websites where you can find interesting projects. I would recommend starting participating in some Kaggle competitions or download some free Google datasets and start playing with them.

For reference: Kaggle is a Google product. You can see the list of current competitions here.

You could try Kaggle competitions, or participating in forecasting markets (as you stated) is another option. You don't need any specific skill set to be a forecaster, the rules of the bet are stipulated and from there it's just based on your ability to predict the outcome. You could also try your hand at investing in the stock market, or try and make money betting on sports games. If you're very good at this stuff I'm sure you can make a lot of money doing it. The thing to keep in mind is that generally video games are much much easier than real life

As to the specifics of your projects, that's up to you. Try browsing Kaggle; check out some of the work we have on The Pudding; check out some journalism examples to see what you can try to build on or improve.

You might want to look at kaggle competitions.