How can potential be defined before defining potential energy? Isn't the potential just potential energy per unit charge? How can potential mean something on its own?
The electric field is a conservative vector field which implies that there exists a function $V$ for which $$ \mathbf E = -\nabla V $$ We call this function $V$ the electric potential. There is no mathematical need to first define potential energy. One can then physically interpret $V$ in terms of a "potential landscape" to get intuition for what it means. In particular, positive charges "roll down" potential hills while negative charges "roll up potential hills." But from a mathematical point of view, there is no need for the intermediate definition of potential energy.