I like getting poison first because its better for constant harass
For top lane (and maybe mid, I don't play mid-teemo), this times a million...for most matchups. There are going to be a few when having that blind is better, but in most, the poison allows for significantly better harass even though Q has more range. But again, for a level 1 invade, the blind would be better generally.
Then again, I also get Move Quick at level 2 because I've learned that if I'm playing Teemo, I'm getting ganked at level 2 and being able to have crazy movespeed is always nice. --- My Superheroes consist of the band members of the Who, Led Zeppelin, and The Beatles