Hello everyone! This guide, split up in two parts, will show you the normal way to play this champion but also the Dark Side of that champion (AP). This part is is about AP Tristana!
You can find my AD
Tristana Guide Right here! http://www.mobafire.com/league-of-legends/build/triFirst Part: AP Tristana
This is the first part of the guide in which I will show you how to AP Tristana :P.
AP Tristana has very high base damages and higher AP ratios than most mages in League of Legends. She can very easily burst enemies from full HP to Death. She is very powerful but very fragile.stana-and-her-dark-sides-ad-214007Let's make it clear that in no way this guide is trying to prove that AP Tristana is better than AD Tristana. The way they are played and the things they can accomplish are so different that comparing them is like comparing
LeBlanc to 
Caitlyn. Both AP and AD Tristana are viable and very fun.Abilities Sequence and Explanation
Draw A Bead:
Increases Tristana's attack and
Explosive Shot range by 9 every time she levels. At level 18, Tristana has 153 bonus range on her autoattacks (703 total range).This is still amazing on AP Tristana. It helps her use
Explosive Shot and 
Lich Bane from a safer distance. Amazing to last hit for a good distance.
AUTOATTACKING IS VERY IMPORTANT
Rapid Fire (Q):
Increases Tristana's attack speed by 30 / 45 / 60 / 75 / 90% for 7 seconds.
Great on AP Tristana late game but try not to get it earlier since the damage increase it will give you will be pitiful and the mana used will be wasted. Once you get level 18 and you get your
Malady, this spell will make you feel like a DPS :P. The spell is also really good to destroy towers later in the game.
Rocket Jump (W):
Tristana fires at the ground to propel herself to target location, dealing 70 / 115 / 160 / 205 / 250 (+80% of ability power) magic damage and slowing surrounding units by 60% for 2.5 seconds when she lands. On a champion kill or assist, Rocket Jump's cooldown resets.
AP Tristana's main skill. It deals tons of damage and also slows. Use it to: farm, kill enemies, gank, jump over walls, jump away from enemies...EVERYTHING.
Even though this spell really does a freaking lot of damage, you shouldn't use it on your enemy everytime it's up because
Rocket Jump is your most reliable escape mechanism. If you jump on your enemy in lane just to harass, and then the enemy jungler comes at the same time to gank you, you're dead. Try to only use it when you know the enemy jungler isn't too close.WHY MAX ROCKET JUMP FIRST INSTEAD OF EXPLOSIVE SHOT?Side note: This skill has its cooldown instantly refreshed if you get an assist or a kill. This is very fun because, if you can make sure your target will die, you can jump back to safety right after killing your enemy. Keep that in mind. Oh and it will also make you feel extremely cool jumping around non-stop :D.
Remember that this ability is not only for damage purposes. You can use it to escape (seriously, people tend to forget that when playing AP Trist).
Explosive Shot (E):
Passive: Enemies explode when slain by Tristana's basic attacks, dealing 50 / 75 / 100 / 125 / 150 (+25% of ability power) magic damage to nearby enemies.
Active: Explosive Shot rends the target enemy, reducing healing and health regeneration by 50% and dealing 110 / 150 / 190 / 230 / 270 (+100% of ability power) magic damage over 5 seconds..
This skill has insane damage at level one (110 + 100% of AP) so you it makes
Tristana really strong at level 1-2. You should use this on the enemy in lane every time he gets in range. This is especially good to counter 
Health Potions because this ability reduces all kind of heals by 50%.The incredible AP ratio makes this ability hurt more than
Rocket Jump late game. Make use of the huge range it has late game to harass/kill enemies from a safe distance.You can this ability first to have a stronger harass tool.
Buster Shot (R):
Tristana fires a massive cannonball at an enemy unit. This deals 300 / 400 / 500 (+150% of ability power) magic damage and knocks surrounding units back 600 / 800 / 1000 distance
Tristana's ultimate deals outstanding damage, especially for its low cooldown (60 seconds). Don't be afraid to use this ultimate very often (yes, even to harass your enemy if you want to). Use it after all your other abilities to kill an enemy insanely quickly.
Make sure you don't push enemies to safety with this. If you still do, at least make sure your
Explosive Shot + 
Ignite will kill them....but really, the damage it deals is just insane...
Runes
Once again, nothing too special, typical AP carry stuff.
| RUNES | |||||||||||||||
Magic Penetration Marks simply because they are the best damage marks for Mages.For Seals,
Armor Seals are almost a must-have right now since there are so many AD champions mid. These runes also help to counter minion aggro and autoattacks in general ( Tristana is fragile)You could also get
Mana Regen/level because it will allow you to spam your spells mindlessly. You shouldn't be but if you have trouble managing your mana, get these seals.. And with your masteries, it gives all the mana regen you need mid and late game.The
AP/lvl blues are pretty much the best offensive Glyphs for casters. They give more AP than Flat AP Glyphs after level 6 only! With them you will definitely feel the neat increase in damage.The other interesting choice is
Scaling Magic Resist Glyphs. Unless you build 
Abyssal Scepter, you have will 30 magic resist ALL game long. This is one of the things that can AP Tristana so risky, especially late game. Scaling MR glyphs can help.The
Flat AP Quintessences are pretty much a must-have. They will really help you to start the game well and will give you that deadly damage you want early game.However,
Movement Speed quints are also a very viable choice as some people have showed me. Tristana is a great roamer/ganker and she has very low base movement speed so Movespeed Quints are really viable on AP Trist. They will help you to get in position to help your teammates out, to chase an enemy, to escape danger, etc.
Master Yi
Katarina
Alpha Strike
Spellsword 
Meditate
Sheen