Hi Lucas, If you wish to improve your imagination: You may enjoy reading, but have you considered writing a story yourself? Why not give it a go and self publish using Wattpad? You can start small with a short story of just a couple of pages and progress to something longer as you get better and better at creating new ideas.

If you want to improve your rhetoric/debate/argumentative ability: Do something different, instead of passively listening to debates, get involved and voice your opinion. Visit Quora and join a discussion about a topic you know about. You could also try reading the books Greeks wrote on rhetoric such as Rhetoric Ad Herennium.

If you want to understand concepts quickly: Challenge yourself to read about something different each week. Especially a topic you are completely unfamiliar with such as Architecture or Philosopy for example. You could then create a video or wordpress blog about what you have learnt. If you can connect new concepts to a priori knowledge you can speed up your learning.

A simple fact to remember, nobody learnt to swim simply by reading books or by watching videos. Enjoy your Mandarin learning!