Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
I only play 5v5. I start off with boots and 3 health pots. I also start with teleport and ghost. Ghost helps me run away or chase down a kill. Teleport gets me back after buying or dieing fast and helps me gank on the other side of the screen.
I play very conservative.
I try to lane with someone who can stun. If I do then I can usually start with 2 kills pretty fast.
With this I port back when I have 1450 gold. I grab emblem of valour and boots of swiftness.
This keeps me in the lane longer with life leech and keeps me alive when people try to gank.
Always line your lane with shrooms. This redirects all ganking people.
If you are lucky you can get a few kills before you port back.
Once you port back you grab Starks Fervor for the attack speed and the life leech for you and your team.
I usually start ganking at this point. I use teleport to get to an area that needs help and has weak people.
Then I buy Guinsoo's Rageblade. With this and starks you can beat most 1v1 battles easily.
Then Madred's for the tank killer. I love the passive here. Plus does basic needed Teemo stats.
I love the crit AS Teemo. I next go for Infinity Edges. Most of the time the match is over before this, but if you have a long match you will shred everyone. If the game goes on forever grab Trinity Force last. Probably will not acquire this.
With Teemo I put shrooms all over the paths that people most likely run. This takes a lot of practice and experience figuring out this. I also use shrooms to put in front of a path of a friendly to help him get away.
Mid to end game I line shrooms through the center of the mid lane and around on passive mobs.
You always have to know when to run away and when to fight. Your team will most likely complain, but you will live and have the ability to defend a turret if your team gets killed. Teemo can not stand in the middle of a big fight and live. You need to strike from the furthest corner and always blind the guy that does the most damage.