For toplane Fizz these are your usual Summoner Spell choices. Most Proplayers are running the Ignite version as it is way easier to snowball with it. Meanwhile Flash gives you more mobility and enables you to dive deeper while giving more mobility. Personally I play with Flash and recommand the players who die to early ganks to do the same ^^.
Masteries are mostly up to you. I would recommend running Grasp of the Undying as nearly everything else isn´t really helping. We are not building a lot of AD neither AP so an offensive Key Stone isn´t helping. Grasp also helps you with Trading and gives you that small perk of Lifesteal in small trades. Instead of 0:12:18 you can run 12:0:18. I prefer 0:12:18 as you are mostly 1vs1 on toplane which provides a good opportunity for Assassin. Merciless helps you to finish low life enemies fast, while Dangerous Game will give you the best opportunity to get a kill and then continue fighting or get out with your
We are mainly playing around using and to get in and out of the fight. Then we can use AAs and W to do damage before retreating back to safety. The decision you need to take is how long do I want to stay in. After maxing W for Trading Damage and Last Hitting we Max E second to reduce Cooldown to have as much outplay potential as possible.
It´s important to stay flexible with your build. Examples here would be : Lanephase is going well you realize you can snowball, building first is the most optimal choice. However let´s say we are laning vs . In other words AD bullies and we are behind. You should then switch your build go for an early and then continue to adapt. If you still want kill potential try . would be good against 3 Aps but in that case you should think about ->-> -> . If the Game isn´t looking good maybe consider going into -> . Never try to build always the same as every game will be different.