Right now this is the easiest champ to play to carry games by far.
If you are sub plat level this is freelo right now.
Hey are you bronze or silver and want out? EASY, no skill champ.

More people are playing him TOP because his Q slow pretty much ensures COMET will hit every time, but BOT lane is the place to carry.

Start Spellthief with comet and you lvl 1 Q will do 148 AP damage.

If enemy doesn't have a support like Nami or Sona their ADC will have to back after a couple Q's with comet or be zoned off farm.

You will struggle with mana issue early but once you drive enemy ADC back, have your ADC freeze and get XP advantage while you back for mana/items.
Try to ONLY use your Q when comet is up.

There are bad match ups I would try to avoid like Morgana and Zyra or if the enemy team has a tank like Trundle.

All these new runes are stupid and give every thing you cast so many bonus effect/damage that you can build tank and usually end up dealing the top DPS in the game.

Once you get your ULT there is no stopping you. I don't care how fed their ADC is, Assassins, Mages anything squishy you will blow them up.

Look at these stats, Malphite's ULT lvl 1 is flat 200( +100% AP) with a 1.5 AOE stun.
Compare that to Malzahar's ULT lvl 1 is only flat 125(+80% AP) single target with a negative energy zone that means nothing.

When you Q an enemy ULT,E,W,ignite/ ULT,Q,E,W,ignite that isn't tanky they are dead.
You usually don't even need ignite, but you have it.
Ultimate hat lets you Ult more often.
Once you have an ult that is on a sub 60's cool down, you have literally deleted the enemy ADC's existence from the game.

Since so much power is in the bot lane right now, you insta removing their ADC whenever you want puts you in a massive win advantage.
Help mid whenever you can, run in and blow up enemy mid laner or force them to spend all their gold on wards.

Have your ADC stay away from River, play to bot.
They enemy jungle usually won't even bother because you will just Q them and get away.

Now, get to it before Rito nerfs COMET into the ground.(Just switch to AERY then)