It may be useful to read Part 0, as it lays out the way the lessons are approached.

Part 0 - Introduction: http://www.oranlooney.com/post/ml-from-scratch-part-0-introd...

Part 0 is fully self contained and it summarize very simply why it boils down to arg min problems.

Some linear algebra basics may be needed to follow the derivation, but with far less prerequisites than anything else I've read.

Please proof read math typos