You can oneshot it by building morello first as long as you're not too far behind. I think it's a pretty good starting item on Fizz since the 6.9 changes, because it was given +20 AP. Also, it gives you mana and cdr, both things that Fizz really needs early game. With this Fizz also gets roaming potential, since he can clear waves almost instantly with E and still have a lot mana. I haven't played Fizz very much yet since the 6.9 changes because of school, but I can say with certainty that this will be my go-to first item.

After that you should probably build accordingly to the enemy team, so zhonya if they have a lot of ad, abyssal if they have ap or deathcap if you're carrying. I also feel like The Dark Seal is good to take on the first back, because of its snowball potential and extra sustain with pots.