Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
You want to E pretty often, it zones the enemy adc off of the cs and makes them antsy. once you land an e follow up by placing a w down then immideitly q on them for some damage while your adc attacks, the plant is ranged so itll attack for quite some time.
In teamfights your goal is to e high priority targets such as assassins or the adc. ult after you get a good e off and place your w rapidly in your ult. q to do some damage and if it turns sour peel for your high priority allies. e chasing enemies and make sure your teammate gets out alive.