Looking at very early data (around 12-15 hours), these are the best-performing decklists right now, according to Legna, Balco, and MaRu's own data-mining.
We'll do a follow-up later today, with 24 hours of data!
It's not news that aggressive lists perform well early on, but 4WL's revamped Pirate build was already wreaking havoc pre-patch – with slight tweaks, it's the best decklist right now, with 600+ games and ridiculously-high (60%+) winrate:
Jhinnie is the most played decklist this early, punching above 54% – another example of how you can't go too wrong by piloting a refined, aggressive list when the meta is up in the air.
She ain't dead… With around 200 games on our data sample (which this early in the patch is quite a bit – the fifth most-played decklist), this Akshan Kai'Sa build punches ridiculously high (60%+).
Too early to tell from the data, but top pilots think it's not a fluke – WhatAmI took this exact same list to Rank #1, and according to Prodigy, "Kai'Sa isn't dead, she is just being played in a very different way than before."
Even Lone Kai'Sa, which arguably was hit the hardest by the nerf, is doing quite well.
Nautilus Maokai, aka Deep
Monte mentioned in Meta Voyage that last week was the best time to play Deep… by early data, looks like he may have been wrong: this is the best time to play Deep!
Veigar Senna, aka Darkness
Quite the expected return – the patch, as a whole, tends to make this a bit of a slower meta, and Darkness received a specific buff.
We'll see where this lands, but currently Darkness performs at 54%.
The usual "too early to tell" during the first week of a patch applies here in spades – samples are small, and brewers have had little time to refine their concept and ideas, so tried-and-true decks have a huge leg up.
Still, if you need to climb (it's a very short Season, after all, and we have Seasonals next week!) the above are the best options right now.
Good luck out there!