The Rune Page for Teemo must contain Scaling Ability power Glyph , Magic penetration Mark and Scaling Armor or Magic resist Seal Runes. For Quintessence runes you can take Sclaing ability power or Magic penetration runes.

When you are at top lane you can farm easily if the enemy dont have pull or jump/dash ability
Dont push the lane and try to harass the enemy when he wants to last hit and dont let him earn XP!
When you are in the Jungle stay in stealth if you see an enemy.First you have to wait until
you can lasthit the Neutral monster (example:Blue Golem) But if you are alone in the Jungle you can use Mushrooms to deal dmg to Neutral monsters and you can use your Q
Blinding Dart to Blind a Large Monster to take less dmg

Pros and Cons

• Teemo is good at escaping
• Ap burst can easily kill Teemo
• Everyone can use Noxious Trap to their advantage
• With Oracle's Elixir or Vision Ward the enemy can found you and your mushrooms

Teemo's Q Blinding Dart is good for poking if you cant harass the enemy with basic attack, but you cant use it to deal high dmg over time with Ignite and your R Noxious Trap.If you want to plant mushrooms without taking the top laner's attention you can use your W Move Quick to go from A to B and back(example: to place a mushroom u use W and use R at the location where u want mushrooms and you can run back quickly).You can use E Toxic Shot to harass the enemy and make a delayed last hit so you can place more mushrooms.

Try to ask someone to take Blitzcrank or a champion with good pull/knockback.If your teammate is low hp and the ADC is coming try to kill him! If you are full hp hide and blind him when he tries to kill your friend!(Maybe He die).With Teleport you and your teammates can teleport to a mushroom to gank a lane or backdoor.

Liandry's Torment can deal lots of dmg with Noxious Trap. Morellonomicon Give you enough Cooldown Reduction with Nashor's Tooth to get mushrooms as fast as possible. Rabadon's Deathcap gives you more than 160 AP and AP makes your mushrooms OP. Void Staff increases Magic penetration so the enemy cant really survive a minefield made of MUSHROOMS.

You can use Mushrooms to farm piles of minions.

Try to lure enemies into the river or where you placed mushrooms.Always use mushrooms if the enemy is a bruiser like Jayce, and try to kite and poke to make easier kills.