Step-by-step explanation:
This is an opinion choice.
Of course, to get an answer to this you will need to make sure you research some of the city states, to get and accurate vision of your answer !
I would recommend heading in the direction of Athens, and Sparta!
BUT !
After the persian war Athens soon started controlling the other city states, making it the most powerful!
I'm not sure what u were looking for here, so I gave 2 answers! =)
Hope this helps!