As a NEET myself I keep my mind active with a wide variety of intellectual activities, from reading to audio books, reading news and articles about astronomy / tech / etc.
Video games help me too, but you have to choose those who will require you to be active, and no passive without thinking. I'm on Surviving Mars in Russia difficulty (330%), and Enderal RPG too.
Writing a book about anything you enjoy will greatly improve your imagination, creativity, mastering your language, investigate about many topics. I've already wrote a book, and I still write many short stories and urban legends.
Another thing is Geoguessr. I'm very strong at geography and it's a game that's really worth the 20$ / year. You're placed somewhere in the world via Google Street View and you have to determine the exact position on the World Map. Which requires to learn about a ton of countries. That's how I went to learn every region of Russia, every Japanese Prefecture, every African country, all the flags, all the US States, etc. I only play on Diverse World maps.
Movies and series are a good way to think, if you choose the good ones. The best was The LeftOvers, who still make me think about explanations. Plus I think it's a series were Incels could find some answers and Blackpill.
Last thing is meditating. Allows you to see how things really are. It's the only way for an Incel not to fall in despair. I even tend to think meditation is the only other way to "ascend". You'll spiritually be way above everyone else, every concept, every idea or every cope. You'll discover yourself huge aspects of what we call the "Blackpill".