Pretty much just the build. Fizz is a pretty easy champ to master if you use E like a pro. Also I don't want to waste time on a full guide when there are a lot out there for him.

PRO TIPS: If you use his E in some creative ways you can get out of a lot of situations with the help of Flash. If you aren't that great with skill shots and tend to miss a lot. Then Fizz might not be the best champ for you, seeing as his only skill shot is his R. This Skill can also get you out of some tricky situations and is a great team fight initiator. Also great for Ganking. Well to sum it all up Fizz can carry a team to victory, or absolutely fail at doing anything and helps the other team win by feeding. Know your limits when playing this champ. Know When to attack and when to just back off. If you play your cards right. You will have the next pentakill with this Amazing Assassin.

Pros

Quick and nimble
Great burst damage
E paired with flash = Almost impossible to catch.

Cons

Kinda squishy unless you build a GA
Skill Shot R, If you miss then...Oh well better luck next time?
Honestly the only thing I can think of is make a cooler Fizz skin.