This build is aimed to make Tristana a scary Critical/Attack Speed focused character by the late game. Tristana's abilities are definitely good, but you get the most out of them if you focus on her AA (auto attack) especially with Draw a Bead and Rapid Fire.
Her other abilities: Rocket Jump, Explosive Shot, Buster Shot all do decent damage until the late game (with the exception of Buster Shot) and are more used for their utility, and by that I mean positioning yourself, clearing creeps, positioning your enemy (respectively).
So having an item set that focuses on auto attack and crit chance (and increased crit damage with Infinity's Edge) as Tristina means that you'll be dealing out a very scary amount of damage per second to other champion's and clearing lanes quickly without having to ever put yourself in a dangerous position against (so long as you aren't being reckless).
This isn't to say that you aren't going to die, of course they're going to be able to attack you with their closing abilities, but my point being is that They have to chase You and it should be pretty hard to finish you off considering the abilities that you have at your disposal.

(editing)

The way to play using this build is to farm as much as possible in the early and mid game and avoid engaging in unsafe fights. **Always keep Rocket Jump off of cool down** You really want to make sure that you always have that ability available to get out of sticky situations (remember you can jump over walls with rocket jump).
What minions you're aiming for changes depending on the situation. If you're running a solo lane you'll want to aim for minions that're closer to the enemy champion in your lane so that the splash damage of Explosive shot will hit. If you're not running a solo lane you want to always aim for the creep that is farthest down your lane when farming to maximize your distance away from enemy champions because for the most part, Tristana is rather squishy.
When you get Banshee's Veil and Cloak of Agility you start becoming more dangerous. If you aren't far behind you can start really applying some pressure to enemy champions trying to push down your lanes and make them turn around.
When you get Infinity's Edge you can really start scaring the enemy team. Your Crit chance gets a boost, your crits do a lot more damage and you get a nice boost in normal attack damage. This is when you are free to become a much more aggressive player, which is want we want from this build.

This build has worked so well for me that I wanted to make it public. I plan on adding more information to this build later.

Also how do you make is so that I can put in info links when I mention an ability?
For instance I type "Rapid Fire" and you're able to hover your mouse over it and it gives you a quick description of the ability.