Ever wanted to melt faces, tank, faceroll, run insanely fast, and cover the entire map in shrooms? Well, look no further, for I have found the optimal build to do it all, and it's really quite simple.

Let's start with the pros and cons.

Pros
-Extremely versatile.
-Great mobility.
-Exceptionally strong lategame.
-Great at poking and kiting.
-Good DPS.
-Quite a bit of damage over time.
-Excels in hybrid AD+AP damage.
-HP/Mana regen and lifesteal allows for more sustainability.
-A healthy bit of tankyness will have the enemy team second guessing themselves, and will save you from a world of worry.
-No glaring weaknesses or easy counters lategame.

Cons
-Very expensive build.
-Very weak/risky early game. Easy to harass.
-Significantly less AP damage than otherwise possible.
-Although very versatile and well-rounded, will never be the best at any one thing.
-No armor or spell penetration can make it hard to excel against especially tanky teams, namely if there's a Taric on the enemy team.

Since Teemo does AP damage with each attack, you'll make the most use of runes by getting Attack Speed marks, ability power scaling quints and glyphs (these will pay off by the time you hit level 7, which will make your ult much more effective than flat runes), and either flat or scaling armor seals, since they are more effective than the magic resist seals.

This tree focuses solely on the most important offensive masteries for Teemo, while vouching for some defense instead of the less useful offensive masteries. You will not need cooldown reduction since your build alone caps you at 40%.

Ignite and Ghost are almost always the best choice on Teemo. Ignite can stack on top of your passive poison damage from your autoattacks, allowing you to really secure those kills that would otherwise be "oh so close." Ghost, on Teemo in particular, is superior in almost all cases to Flash. It has a much longer effective distance, a much shorter cooler, and combined with your W, it will be an easy escape and an amazing tool for chasing and kiting, allowing you to get more attacks off while chasing someone running away from you, and allowing you to keep distance on a bruiser trying to close their distance between you while you still attack them.

This may seem like an odd start build, but trust me. You will want to start with a single sight ward and start your Kage's Lucky Pick. You will need the sight ward in case of an early gank, and the ability power will help you pack a little more punch with each autoattack. You'll want to play safe, last hit, and farm until you hit enough gold to buy both your Kage's Lucky Pick and Philosopher's Stone, and then try and blow through your mana and some excess health by poking your lane enemy, and return to base and buy, then quickly W and run back to lane. The philosopher's stone will also help you to sustain slightly.

Nashor's and Berserker's Greaves are an absolute must on Teemo, since most of his damage is on-hit magic damage. Nashor's will give you a huge 20% CDR, 65 AP, and a huge boost in attack speed. Berserker Greaves will give you decent attack speed and more mobility, which will make kiting, chasing, and getting out of Dodge much easier.

Now this is where things get funky. You'll want to keep your Philosopher's Stone until you hit level 15, and upgrade it before you hit level 16 or the passive on Eleisa's Miracle will become useless. If done correctly, at level 18 it will act as a seventh item in your build, giving you mana and health regen you otherwise would not have. If the enemy team has a lot of AP damage, you'll want to rush your Guardian Angel. This increases your MR and gives you a free revive, buffing your global taunt drastically and allowing for your team to get some nice free kills in teamfights. It even gives you a chunk of armor, which you will absolutely need since Teemo is so squishy. You will then want to get a BotRK, since it will allow you to shred through anyone on their team, no matter how tanky, in just a matter of seconds, and give you nice hybrid damage and even a little bit of lifesteal. You will then want to get a Rabadon's for obvious reasons, and then finally finish off your build with Morellonomicon. With your extra gold, buy some potions.

Last hitting is crucial. You'll probably spend the first 20 minutes of the match pushed to your own turret, so you'll want to learn how and when to last hit even if your turret is trying to steal your farm. If you fall behind, it will be extremely hard to catch up, but if you manage to farm enough, you could snowball into an unstoppable killing machine.

In conclusion, all I have to say is this is a build you have to try for yourself to truly appreciate, but the math does not lie. It will throw people off, make it very hard and often costly for an enemy team to counter you, as there will be no one way to do so, unlike with flat AP Teemo in which he can be countered by a simple 400 gold Oracle's Elixir. You'll have a healthy well-rounded amount of HP, AP, AD, mobility, unique passives, armor, and magic resist, where other Teemos will be much more weak in many aspects.

Have fun!