Tristana is not a champion with high survivability but if played right u wont die many or even any times at all.
This is a DPS build for Tristana. its mainly used for 3v3 but if too har dto farm the gold for it go 5v5.

Pros:
Good escape mechanism
Very high dmg at late game
Good ganker
good combo maker

Cons:
Squishy
Hard to farm with in beginning
if disabled easy target

These masteries is the best do incre***e your DPS ratio.
If you use diffrent summoner seplls u can take out one point or more out of the utillity field and put it on the summoner spell mastery.

Flash: This is a good summoner spell on most champions on Tristana you use this and then use rocket jump for a 99% catch of the enemy champion.

Ignite: This if for that little extra dmg if u cant catch your enemy or if she/he is tanking. In many cases u can just simply use this as a dmg output

I use these items to get a good dmg and attack speed this is not a build for survivability flash and rocket jump takes care of that.

Dorans Blade: good start

Berserker Greaves: u cant make it through any game without shoes and this is the best choice for tristana.

Phantom Dancer: incredible attack speed, crit chance AND movementspeed nuff said.

Guinsoos Rageblade: this gives u both dmg and ap and is a good choice for harassing enemies
the ap is for a little magic dmg in spells. The passive is like the icing on a cake, Tasty.

BloodThirster: If u die very often reconssider this item. This item gives very high dmg and lifesteal which is necessary for any DPS build. The passive of this item is just amazing if u can survive it can give you 40 more dmg and 10% more lifesteal.

Black cleaver: more attack speed and dmg. As a bonus the passive gives you a pretty high armor penetration.

Madreds Bloodrazor: gives you a Dmg, attackspeed and even armor: the passive is for those pesky tanks. if u want u can witch this item for infinity edge