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.
The idea is too early spam spirit fire to gain gold and damage opponents.
Wither to either slow opponents when attacked or to gang.
When you running low on Mana or Hit Points the idea is to TP back and forth to tower to keep the gold and the exp flowing.
The important thing is to be able to assist more than kill so team play is most important. Therefore Mid and late game the idea is to lure the enemy to attack you. Once being chased or attack you retaliate in spirit fire and switch on ulti mid way in the battle. Wither to either slow down the attack rate or to chase.
Cleanse just keeps those nasty stuns and last second ignites away. Helps throwing champions off guard when they have the upper hand.
Once you get to aegis your item build should be situational. If it’s a balanced team the build should work out.
If there is more stun and ability power opponents consider building a Veil.
If there is more attack damage\attack speed opponents consider getting a frozen heart.
So let them underestimate you till it’s too late.