People will think that an AP Tristana in the JUNGLE is the dumbest idea ever. I'm a jungle only player in 3v3 and I jungled almost every champion, there are some champions like Annie or Galio that you would never try out in the 5v5 jungle, only in 3v3. AP Tristana is really really fun to play and has probably the highest burst of all champions in the game. I first got the idea of AP Tristana in 3v3 when I was thinking of useful assassins that can 1v1 the most popular 3v3 champions, but those are all melee, like Kha'Zix, Zed, Evelynn or Akali. They all have certain problems getting their damage off and most of them need a few seconds for their burst, unlike Tristana. Her ultimate and E scale INCREDIBLY well with AP, she can stop lifestealers and healers with her E passive. The only reason why I tried out jungle AP Tristana is because I'm a jungler, and it worked better than I thought.

Pros:
- Super fun to play
- 1-hit potential against carries <100 MR
- High ranged burst
- High base damage
- Easy jungle clear
- Amazing ganks and poke on lanes
- Especially strong in 3v3, like all assassins because of one-shot abilities against a small team

Cons:
- Not really blind pick (unranked) viable
- Wooglet's Witchcap and tanks counter her very hard so that's she's almost useless in teamfights, in ranked you want to pick her as a last pick
- Squishy
- Not made for long teamfights
- You have to sell Spirit Stone because the upgrades aren't worth the gold
- Needs farm

I tried out the Doran's Ring and pots start but I failed. Then I had the wonderful idea of beginning with a Spirit Stone like the most junglers because: Tristanas Rapid Fire increases her attack speed by 30%, the Spirit Stone increases her damage output by 20% vs. creeps and she gets 10 extra damage per attack. She also has 50 attack damage. That makes 72 damage per attack. Sped up with Rapid Fire she does some quite awesome damage. You want to take your Explosive Shot as your second skill because you deal extra damage with the ability and AoE damage when you lasthit a creep. Take Rocket Jump third for ganks.

Items:


This doesn't help you in the jungle but adds very high damage against champions.


This is the main item for an assassin AP Tristana. It gives burst for your ultimate and absolutely everything that Tristana needs. This is much better than Wooglet's Witchcap and costs even less.


This item is very amazing as the second item in your build. It multiplies your AP from Blackfire Torch while scaling very well with AP. It also makes you a save rocket jumper because of the active.


This item is very good with Explosive Shot because the ability refreshes the passive. It also gives magic penetration which is good against squishies or champions that build HP. Most teams have some slow or CC anyway so that Liandry's Torment deals double damage.


The extra mana is amazing. Like the old AP Master Yi tristana needs a lot of mana because her Rocket Jump refreshes when she gets kills or assists. The passive adds extra damage to her burst and improves her damage in longer team fights.


Tristana should not have to buy this item. You should pick 2 AD champions in an AP Tristana compilation so that she can burst tankier champions that have a lot of HP but no magic resist. She basically deletes 1 champion from the enemy team. It's still a good item when people have around 100 magic resist because you reduce it to ~20 magic resist with the flat magic pen that you have from runes and items.

Jungle route:
Start Golems, smite early
Move to Wraiths, get level 2 from Bigger Wraith
Move to Wolves
Do Golems again with Smite
->3:00 take your altar

As AP jungle Tristana you want to recall very early and gank on level 3, you also want to get the Ghost Relics. When you reach level 6 you want to spam your first ult in the toplane and get a VERY easy kill. You can jump over the middle wall, which is the second thickest wall on the map and help your top laner with the first blood. The enemy will not expect that, trust me.
In mid game you want to snowball very bad from both lanes and spam your Explosive Shot in lanes whenever you can since it deals amazing damage and helps your laner win the lane.
In late game you have only one goal: You want to kill 1 enemy champion with your combo and disengage very fast OR you want to jump around and deal some extra damage, then use Wooglet's active. You want to trade your life for the life of the strongest opponent if you have to.