This is my own quick test build reference for Tristana.

Runes are just high enough to get 100% crit rate with IE and 2x Phantom Dancers. HP5 for lane dominance early game, and AP for those times when someone escapes the Jump/Explosive/Ignite/Buster combo with like 5 hp.

Pretty much standard masteries.

The item choices are for a crit auto attack based build. Various ways to build up to the start, but getting a [Doran's Shield] followed by [Boots of Speed] and 2x [Doran's Sword] is a good way to start. You can replace the shield with another sword if you know you will be paired with a supporter with a heal at the start for more damage.

Building up to [Infinity Edge] is paramount, usually [B.F. Sword] or [Pickaxe] is a solid way to start. [Berserker's Greaves] can be gotten whenever it feels right really, though you probably want at least one solid AD item before you do it. Once you have IE, [Phantom Dancer] x2 will make a huge baseline damage that will lead you up to 100% crit rating, and to the point where you can start making team fights turn into your team's favor. [Last Whisper] is a late game item for when people actually start building up some armor to take them down faster. As for the sixth item, it can be quite variable. Anything from [Madred's Bloodrazor] for damage, [Aegis of the Legion] if you need some more HP and Resistances, or even [Tiamat] if you need to help fend off a huge creep wave at base. These could also replace LW for 5th, moreso for a defensive item if you need one. LW generally adds quite a nice chunk of damage.

Skill sequence comes mainly from reading other guides. Main things I shoot for is level 3 [Explosive Shot] and [Rocket Jump] to build up the burst with [Ignite] for early kills. Level [Buster Shot] as available to add to your burst damage and help stop ganks later on in the game.

Ignite is pretty much a must, for early game kills. This can easily net you an extra 1k in early game kills with a bad opponent, or keep a good one on their toes. As for the second, [Teleport] if you like map control, [Flash] for an extra escape or a way to slide in closer to an opponent.

Make this later.