Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Okay well I know this isn't the best build but every time i play it, I usually go around 13/3/15 so it's a good start.
Early game: You will want to buy Shield and a Health Pot.
After you've gotten at least a kill or Maybe Assisted or Killed a couple minions you have enough for Berserker's Greaves. I usually just get them for the attack speed. :P
then you should be good until you have enough for the malady.
Mid Game: After you've ganked, gotten some kills/***its you should probably try going for a Black Cleaver. That should boost your damage a little more for Faster kills. (Btw Don't go ganking until you are about lvl 10 or higher)
Late game: Once you are around level 15 you should probably have Frozen Mallet by now. And then go back and Aim for an Infinity Edge or Phantom Dancer. Either one works at the time. By Level 18 You should have it all set up (Not including the Shield)
Tristana is all about Attack Damage, and Attack Speed. Her abilities use a lot of Mana so make sure you use the right Ability at the right time. For her abilities you should mainly use "Rapid Fire" For taking down turrets or any other buildings. Rocket jump would be used for Ganks or getaways. Explosive Shot: Just your DOT ability That helps when they have around a little less than half health (: Buster shot would be for if they are about to kill you and you can just blast them back. OR you can use it for pushing them towards your turret for the extra damage. OR if they have a little Health left and you just want to end it quickly. She can also be good in early game by Soloing. In Mid or Later game you should Assist Allies.
Now for Buffs, You should start out with a Lizard buff just for the extra Damage. Then later on you should aim for A Golem Buff cause she can run outta mana Quickly.
If your team decides they wanna take Baron later on. that'd be great for Tristana.
Well thats my Build and I hope you have fun with it.
Comment telling me if i need to Improve anything. Or if you have any problems with it.