Tristana rune build idea
Sorcery + Precision
Arcane Comet is the keystone, effectively giving you a less reliable Electrocute when you use your E. This is followed by The Ultimate Hat, which gives 5% CDR to her ult (and stacks on usage, up to 15% in total) for bursting or protection. Transcendence gives her 10% overall CDR, making it so she only has to build
. Finally, Scorch works alongside Arcane Comet for additional damage. With Precision, Legend: Alacrity and Cut Down (against Tanks/Juggernauts), Overheal (early game synergy with Soraka/Sona), or Coup de Grace (for ganks/all-ins) are used to help Trist's late game.
This build is based on giving Tristana more of an early presence advantage while building her CDR and Attack Speed for late game. Items used should be based on giving her the most damage and Attack Speed she can get (specifically, building Crit). Transcendence and
grant 40% CDR without building separate items, and her other items should help with her damage output and taking down single targets (

). Her next item should be
, and her last item is based on which Precision rune you picked (
with Cut Down,
with Overheal, or
with Coup de Grace). Which one you choose is your choice.
This build should most definitely only be used as a Bot Lane ADC, which means you will have a Support. Which ever one you have should have enough utility or offensive presence to make it easier for her to snowball. Sona and Blitzcrank are two very good examples of Supports for this build; Sona is especially helpful if you chose Overheal, since she already gives both a heal and shield — which means that you're getting two shields in one when at max health, and combining this with
only adds more to that. Shaco, Heimerdinger, and Teemo are incredibly useful when you have Cut Down, as their traps (and in Teemo's case, overall damage output) are effective at quickly chipping the opponents' health down.
One of the drawbacks of this build is that it doesn't have access to Future's Market from the Inspiration tree, which would give you some leeway on building in case you're behind. It also keeps her from having other keystones that she would otherwise like to have (Electrocute from Domination, which has a long cooldown but guaranteed damage, or Glacial Augment from Inspiration, which gives her some utility for an offensive support or ganker to take advantage of). Another drawback is that building Full Crit is monetarily costly to be effective at all, forcing you to snowball or bust. However, there are many pros as well. The combination of Arcane Comet and Scorch does more combined damage than Electrocute during early game (which is where you need it the most), and the Sorcery tree gives her more safety than Domination provides. While the Inspiration tree offers utility (one of the runes also affecting CDR), it does so without giving her the safety or damage from this build. Finally, while she doesn't have access to Future's Market, smart gameplay should make that unnecessary.
Give me your thoughts on this build!