Whiteboard exercise: On a scale of 1 to 10, rate your knowledge of, and confidence using, complex numbers.
Introduce Argand plane, equivalence of $a+ib$ and $\left| r \right|e^{i\varphi }$ forms. Euler relation. Practice geometry: $a+ib$ is $a$ along $R_e$ axis and $b$ along $I_m$ axis OR $\left| r \right|$ rotated through angle $\varphi$ from $R_e$ axis.
Addition is easiest in rectangular form; multiplication in polar form.
Complex conjugate and modulus; rationalizing fractions.
Equating complex numbers gives $two$ pieces of information.