Let me introduce myself i am a gold II EUW player.
Teemo might be the most hated char of all times, he is a sneaky yordle and ready to shroom your hearts
(I am joking he will blast you away and stop taking shrooms you blind fool)

Pro side:
Ridiculous dmg
Passive to be a ward
kiting master
Can turn teamfights with ruuans

Cons:
They will call you a troll
squishy at early lvl's
Gank potential pre 6 is quite low
You will be targeted in tf's even if the enemys all die because of that because the hate you

I would recommend you to take red first because it will increase your early damage a lot. then clear a camp until you get to the blue. After blue you will be ready to gank or just continue farming if it isn't needed.
Kiting is your bread and butter run away from the golems and if they come near just blind them.
After your first back you won't care any longer for the creep dmg because you will be healing yourself
(and you won't need blue because of that hehe...)

You can take out any adc and win even 2v1s if you farmed properly
Shroom warding and your top laner was never ganked again muhahaha