12.25Secondary dominant into ii–V–I

One of the most useful patterns:

V7/ii → ii → V7 → I

In C:

A7 → Dm7 → G7 → Cmaj7

This appears everywhere.

Try it.

Then add tonic before it:

Cmaj7 → A7 → Dm7 → G7 → Cmaj7

Very useful jazz/pop progression.