Desert Island Math, April 18, 2022 (Shortest distance)
We strongly recommend Tristan Needham’s Visual Differential Geometry and Forms: A Mathematical Drama in Five Acts. This book is quite advanced, but has lots of excellent prose and brilliant diagrams and will be something that you can read and reread and continue learning from.
A less advanced, but not easy book is Stories about Maxima and Minima by Tikhomirov.
I used many Geogebra files to do this program, but the most useful one to share with you is the one that constructs the Fermat point of a triangle.