Welcome to my Guide!
The idea of Fizz toplane is not really a new idea of the Champion in general, but to my mind, Fizz falls off Lategame, because he is too squishy and can get "cc" out and shutdown easily in teamfights if fed. After some practice and elaborating the build on toplane, i came to the conclusion, that he is not only a good bruiser aswell as still a high damage Champion, which doesn't fall off in teamfights.

Pros:
- High mobility
- High burst
- Easy farming

Cons:
- Usually Squishy
- All in or nothing (no poke) "GO HARD OR GO HOME"
- Almost no "cc" (only with his Ultimate "R")

Barrier: A good skill for some more survivability and All ins
Ignite: Explains it self. If you All in you want to make sure you get the kill 100%
Matchup dependent:
Ghost for the chase.
Flash for more escape-ability if your "E" isn't enough

Marks: Here i choose the duo-penetration marks, which comes greatly along with Fizz' Q and his W. This can deal early- to midgame true-damage to the enemy AD-Carry or even against squishy toplanes.
Seals: Flat Armor. Mostly common against the most AD-Bruiser.
Glyphs: Scaling Magic Resist- This is for the mid- and lategame important. If you're against an AP laner think about Flat Magic Resist Gylphs.
Quintessences: Flat AP - just for some early basic scaling on the W.

9/21/0
On masteries i usually tend to go on survivability, as a bruiser to be more useful and have to care less about "cc".
Thats why i pick the mastery "Relentless" with 2 points which reduces slow effects by 15%!
So even if you dodge one or two skills with your "W" you can expect more "cc" raining down on you in teamfights, especially with the current meta, where the top tier team compostions remain on "hard cc".
The masteries "Unyielding" and "Block" are a really good addition to Fizz' passive.

Starting Items: I am a huge fan of the "Doran's"-Items. They offer you survivability but you should keep in mind that they wont save you against high burst and might cripple your earlygame because you're lacking health pots,so if you're playing against bursty matchups, stay safe and buy boots 3. Vision is nesescary against the enemy Jungler, but with your "E" skill you dont have to worry much.
Core: The IceBornGauntlet is a MUST HAVE in my opinion. It gives you "cc" with every "Q" skill and armor. Even sustain with the mana for some more spamming of skills. Bruiser enough? Not really, so get another "Sunfirecape" or a "Warmogs". This gives you the extra HP you need and with the "Sunfirecape" some more extra damage.
A "Wits End" gives you the extra Magic Resist you need and a good amount of attack speed. As the "Blade of the Ruined King" its passive will proc everytime you "Q" through someone. The extra attack speed is a pretty good addition to your "W" to get more "on-hit" damage.
The "Hextech Gunblade" is a really good sustain item and good for chasing down kills with its active.
Boots : This is really dependend on your playstyle/matchup. Want to get less damage from "AA" get "Ninja tabbies". "Mercury's Treads" for even less slow OR if you want to roam alot to help out other lanes, get some extra movement speed!

Usually Fizz has a really good laning phase against melee champions. He can farm easy and doesn't get poked too much.
Singed: With your "DOT" of your "W" you can easily keep him on low health. Your Kiting possibilities are endless with your "E" and "Q". Just never get Flung!!
Darius: If you can dodge enough of his "Q" you can easily survive and burst him even more with a combo than he does post Level 6.
GP: This can be abit hard, you dont have enough potions to survive many of his "Q" you might loose here. But when it's about all ins you win. Your "W" applies a greavious wound which halves his healing from his Oranges ("W").
Nasus: This is pretty easy. If you cannot deny his farming, just kill him. His passive lifesteal is, again, useless against your "W".
Mordekaiser: Dont get poked and attack him with you "W" as much as you can and finish him off after some time.
Akali: Pre level 6 you win easily. But after she hits 6, she can kite you even more than you can with even more burst.
Irelia: This is a farm fest. This matchup is about skill and who brings better plays or has the better jungler.

WARNING: Fizz being a counter to something doesn't mean you instantly win. It just makes your early game easier. Please do the league community a favor and don't instalock Fizz even if you didn't play him before.

Thanks for reading and enjoy your playing and hopefully owning on top!
Good luck, Summoner.