this is my new way of playing tristana its more aggressive than before. hope you like it :)
for my runes i use armor pen marks. attack speed seals. and attack damage glyphs/quins. its simple and effective in early game.
i use a pretty standard 21-0-9 setup picking up utility master for when i grab red buff.
this build works in any lane and is strong late game. i start with a vampiric scepter to ensure survive-ability. next i get a dagger and up my attack speed. the dagger builds to berserker's greaves. now if you are doing well you would buy the four dorans blades, if not then skip that part cause it will slow you down. if you do buy the blades sell one at a time to build items to keep your lifesteal up. next you buy a long sword to add to your damage, this builds to a madred's razors. now you don't want to sell any more dorans blades so just save gold to finish madred's bloodrazors all at once. to build the next item you don't need to sell a blade because it uses the vampiric scepter. all you do is save up for a bloodthirster. next i sell a dorans blade and buy a zeal, it builds into phantom dancer. i buy a pickaxe and build last whisper to up my armor pen and stack on damage. now you sell the last blade and buy a b.f. sword. you build it into infinity edge so your crit chance increases. your crit damage will also go from 200% to 250%. now you have used all six item slots but i find that with phantom dancer you don't need berserker's greaves so i sell them and buy recurve bow, i build it into starks fervor for the added armor pen, lifesteal, and attack speed.
with tristana i always get her explosive shot first because its good for control. its a dot(damage over time) ability that kills health regen. the next ability i unlock is rocket jump because it has many uses(diving, ganking, running, baiting, and trapping) jumping over walls is something unique about this ability. also as she levels her range increases so your jump distance increases as well. at level three i unlock rapid fire. its good for pushing turrets and killing champions that might get away. i work on maxing out rocket jump because it deals the most damage. i pick up her ulti(burster shot) which physical and magic damage while pushing its target away. the next ability i max is rapid fire because with it you can down turrets fast and push hard. i do pick up a few more levels of explosive shot along the way for the dot damage. lastly i finish explosive shot and burster shot.
normally i like to use flash and ignite because a good combo is rocket jump in(near their turret) explosive shot and ignite then flash out and pick up an easy kill. you can also use the flash to escape an enemy then rocket jump back on them for a kill. if you are in a position to get fed picking teleport is good so your always in the fight.
in team fights i would try to stay back and let my range do all the work. when you see a low health champion jump on them because getting a kill or assist resets its cooldown. if an enemy is trying to get away jump on them and rapid fire for the kill. if the other team has a tank hit the tank with you explosive shot so they don't regen health. if your team is loosing a fight use burster shot to keep the enemy out of range of your team.
just farm creeps and save mana and abilities for getting kills. vampiric scepter is good early because if you take a hit you can regain you health by auto attacking creeps. rapid fire is good for downing turrets and rocket jump is good for jumping into an enemy getting the kill and jumping out, or getting away fast. if you didn't know rocket jump lets you jump over walls. explosive shot is what i get first because its passive ability damages and kills creeps making it easy to get ahead in faming. your ulti(burster shot) is useful with rocket jump, if you jump past your enemy and use burster shot you can push them towards your teammates.