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.
Teemo is relatively squishy, but the tank talents help. You can opt for hp quints as well, if you prefer.
Early madreds makes farming easier. The biggest issue here is the lack of lifesteal so keep that in mind, save blind for melee carries and shroom everywhere.
Remember, the poison from shrooms does not stack, so stagger them out in popular runways, the enemies will be cursing your name when they run into the third shroom in a row and have to back.
They're also excellent scouting tools and great for leaving a trail behind team fights. Only use them on minion waves if it's a big one about to attack the tower or if the enemy is likely to dive in so the creeps need to die fast.