i mean if you're a bruiser concede the wave until level 3 cause in 99% of trades you cant fight back before then, without cheesing. like you'll win the initial trade but start losing once youre backing off. plus its not a good idea because you might also accidentally push the wave to them, thus denying you more.
therefore, let them slow push the wave into you so you develop the minion wave advantage, and trade then. as long as you quick trade then back off they wont follow due to the fact they will take a bunch of winion aggro. once they burn a spell to begin thinning the wave, proceed to go back in. ezpz escpecially if you start doran + second wind, or take TWT + BD in inspiration, and you can sustain right back up.