Please study first the thinking course. It is easy and quickly teaches good quality common sense like objective thinking skills that are a good groundwork for one's intelligence and without which it is difficult to reach any kind of quality in thinking and intelligence.
After studyi8ng the thinking course, you can develop in intelligence by reading the some 300 (mostly soundless) text videos on the playlists Increasing intelligence and Rationality of feelings at my internet video channel http://www.youtube.com/khtervola . Just bladdre the names of the videos and watch those which interest you. The video lists haven't been arranged in any way. See maybe also the playlist about Masterful skill.
In Finnish language there is the original version of this block which is much longer and has some texts in English too: http://pikakoulu.blogspot.fi
About intelligence at large, see http://intelligencelevels.blogspot.fi
23. of December 2018 One can learn good quality for thinking also by reading Kalevala, the Finnish national ephos, an old collection of poems, formerly transmitted from mouth to mouth, but it is in Finnish and difficult to translate. I have tried to translate the beginning in a climate free way, you can read it at http://kalevalainenglish.blogspot.com/