There is alot of ****ty Tristana guides out there who are made by players who have no idea what they are talking about. For this guide i looked at all Tristana's pros and cons for example what she scales with and stuff and i ended up with this.
I've won so many games with this build and currently my Tristana in ranked winrate is 86%.
This Tristana build is made for people who try to hyper carry late game with her and even early game.

Tristanas win conditions are
Early game:Push with the help of your E (explosive charge's) passive and hit level 2 before the enemy once you have done that tell your support to engadge so you can get first blood.

Mid game:Tristana is really strong Early and Late game but falls off mid game. All you need to do is splitpush as much as possible in midgame and get as much farm as you can for lategame to carry

Late game:This is where you carry your range, damage, attackspeed, Is way over the top compared to other adc's. All you need to do is make someone in your team engadge and then you land an explosive charge on someone in the enemy team and keep your Q activated.

In the current meta adc's are about pushing down towers wich Tristana is the best in by far.
Tristana is also a unstoppable killing machine because her Dps is so over power.

As Tristana always try to use your W after a fully Popped E To double the dmg In teamfights try to land explosive charge at their carry wich Tristana is probably going to be able to do because of her range late game.
Since your W resets after a kill try to use it in the middle of the enemy in a teamfight in order to get a kill since you know you can just jump out of there later.