I am Golden Cat Gaming (OP.GG: https://na.op.gg/summoners/na/gr8andpwrfulnub)(Twitch: https://www.twitch.tv/goldencatgaming1), a Yuumi OTP, who also plays Lillia, Neeko, and Nami. I am Bronze ELO and trying to improve to Gold.

S tier - Both Yuumi and Vayne are both great scalers, so you just need to survive the early game and maybe get a couple kills.

S tier - Jhin can do a lot of damage, with very strong scaling. Level one, you are a little vulnerable, but who's not? Level 2 is when the duo turns on, if Jhin levels up his w, Deadly Flourish, you can catch the enemy out with Yuumi q, Prowling Projectile and Jhin's Deadly Flourish.

S tier - Like Vayne, Jinx is a very strong late game scaler, paired with Yuumi's w, You and Me! maxed out, this is an insane duo late game.

S- tier - Yuumi is not as strong as some champs with Tristana, such as Braum or Nautilus, but if Yuumi maxes Zoomies and You and Me! to keep Tristana alive, you have a pretty good chance of winning fights.

S- Tier - Insane lane sustain and poke pre-6 and a very safe all in post-6.

Locket of the Iron Solari is a great teamfighting item that applies Ardent Censer, Chemtech Putrifier, and Staff of Flowing Water, except it does not scale with heal and shield power. I do not recommend building it first, and it is a very situational item. Note that I am still testing Locket of the Iron Solari and none of this is finalized as of right now.

Luden's Tempest is an extremely fun item if you want to have a good time, or you need some ap on your team. Or you are like me and forget to change runes. I definitely don't do that half the time.