You are entering a guide assuming you know how to play Teemo, this is merely a build, not a lesson. I love you all the same anyway and NASA appreciates you too.

The above selected runes are made to keep you alive and hurt, pretty simple shizit.

Ok so, I like to mix it up a bit here and go 26 into offense and 4 utility. This is so you can dominate your lane, assuming you are Teemo you will be the pokemaster and deny farm early game with ridiculous amounts of harass.

Start with your normal boots and pots, unless you feel like the top you are against has no way of touching you, then take a dagger and a pot and harass harder.
Get that Nashor's tooth asap, then follow it up with a Wit's End. You will hurt quite a lot from those two.
Next up would be your runnan's because teamfights should be breaking out now.
end the game with your Liandry's and Rabadon's. Somewhere in the middle of that get your second tier boots depending on your lane match up. (ie: auto attack heavy-ninja tabi, easy lane-berserker/sorcerers)

So basically the game should begin with you harassing your lane indefinately, denying loads of farm from your enemy and forcing the jungle top lane. This will allow you to potentially get fed, but also ease up the other lanes due to their lack of a jungler who is living in top lane. At 6 start filling the bushes with your NASA probes. Once your teamfights break out, jump on in there and let em' have it with your runnan's. other team will surrender at 20 so no need for late game.