Very interesting build and one which I will definitely be attempting in the future!

Love playing Teemo; ever since I first picked him up a month or so ago. Wonderful balance of annoyance to the other team, damage that persists and wards that pack a punch. One thing I could suggest is in the placement of shrooms; I find it useful to think about where I would run to if I was on low health and wanted to port back. If you manage to find yourself in enemy territory these are the places shrooms are best for a sneaky kill.

MPen is the right way to go. There's a misconception that oracle's nullify teemo's shrooming but thing is that Teemo players should always prioritize shrooming bushes over shrooming the sides of a lane, because #1 aside map awareness it twarts and punishes gankers and #2 someone with oracle won't know a shroom is there till they walk inside the brush and when that happens the bomb detonates.

Oracle's do get annoying and can rob you off bombing enemies at certain places not covered by brush but its by no means a complete solution

Masteries have changed. What would you recommend with the new setup?

This guide is from about two years ago.

A whole lot of things have changed since then. Good luck finding dodge yellows, for example.....