I will keep it short, and tell you a few things about myself. I'm a multiseason
consistantly master or above jungler and coach on EUW. I've been playing Lillia since her release and gathered probably something like +/-3000 games on her while still playing a lot of other champions through the seasons (Such as udyr, hecarim, eve and so on), I'm not a onetrick though, I just always enjoyed playing Lillia because of her super high tempo and posibilities to turn around certain fights.
Make sure to check the notes on the items, there is a LOT of useful information that will help you learn how to build and play Lillia. You can check out my stream here. https://www.twitch.tv/yeeter_1v9

Lillia's strength comes from her mobility and high uptime kit. The build options are limited to a certain degree for her in season 12. She can choose to bruiser, more tanky or full on damage. You can build offensive or defensive, farm, counterjungle or gank, engage on the enemies or peel his team and so on. Her downside is that she is not able to make an impact like other champions, especially since she doesn't have an amazing gank pre 6. To achieve victory as Lillia you have to build the game from the ground up with repeated low to medium impact abilities.

Vs CC comps = If they have hardcore CC with undodgeable stuns such as Nautilus auto and so on you can choose to either go double tenacity in your runes by choosing Unflincing in the resolve tree, or you can choose to buy mercs to reduce their CC.

Vs mostly AD comp with slightly or behind AP dmg dealers = Just the classic build but you can choose to sweep in a spirit visage to get a little bit of MR while still staying tanky due to the HP it gives and the increased healing for your runes, conq and your passive.

Vs FULL ad comp: Demonic - Jaksho- Deadmans/Rylai's/Frozen heart - Rabadons - Boots of choice CDR/Armor/Pen boots.

Vs FULL ap comp: Demonic - Jak'sho - Abyssal Mask - Force of Nature - Rabadons - Cdr boots or Mercs if they have heavy cc.

Rylais is a new addition which is very good vs short ranged champs or to cut off mobile champs for sticking onto you and your team.

As you start the game you practically want to ignore your team. Don't get baited by their pings into unneccessary ganks cause your champion can't early gank 99% of the time and even if you get the gank off and it works its simply not worth it. Keep on fullclearing untill you get a perfect opportunity for a counter gank, or a really free gank.

You're playing to scale when playing Lillia so keep you in tempo and CS and stay relevant in the game by not doing too risky plays.
Later in the game you want to keep up your 4 Stacks majority of the time when about to start fights so you can dodge abilities and get in a perfect angle to get a good ult off.
Be careful about using too many abilties as you can quickly run out of mana in the fights, and by then you're going to be useless.

When you have all 4 stacks you can kinda zoom in and out and stack conqueror slowly waiting for them to badly engage due to being afraid of the engage from your team / yourself.

This is bruiser Lillia, you can tank a lot more than normal and you need to play according to your build which is kiting, playing slow to stack Rift+Conq+Stacks to maximize your damage output in teamfights.

Tierlist for Lillia's matchups | S are the easiest matchups and D are the hardest matchups.

You want to avoid fighting early most of the time unless you have a really strong Mid with prio who can CC so you can ensure that your W hits in the middle to maximize the damage.

Setup early vision vs Nida, elise and so on to make sure you're not getting invaded and if you're you can make it out in time.

If the majority of their team is Physical dmg but they have hard burst jungler such as Diana, Evelynn you can build a Negatron Cloak before building your Frozen Heart.

How to use Lillia's kit to her maximum potential:
Q: You want to keep up your stacks, and kite back and forth to hit with the edge of your for maximum damage. If you face melee champs you can space them with your Q and hit them with edge and kite back and forth to confuse them, and they won't be able to get in range to you (most of the time) if you perfect this.

W: Lillia's W can either be a very worthless ability or a rather strong ability if you use it correctly. Most of the time you want to wait untill they are mid-animation with either an auto attack or a ability to try and hit the middle part for most dmg. Often waiting for them to be CC'ed by one ability or another can be a good way to make sure you hit it. You can also use Lillia's W for the small dash it has to avoid getting hit by abilties such as Lee Sin Q to clutch a fight. You can also jump very small walls such as the wall at wolves if you stand at the thinniest side of it and use it the right way!

E: Lillia E is a neverstopping little bloom of damage that can travel as far as the map untill it hits an object. You can use this to keep up your stacks while chasing someone or getting around the map by throwing it over the wall and hitting drake/krugs and so on. It has a weird AOE hitbox and if you get better at knowing the exact hitbox you can sometimes use your E on a wave from a certain angle and hit the people behind with it to start off the (team)fight.

R: The way you want to use Lillia's R is more a defensive way than an aggressive way. You have to be patient and way for the right moment where you can get a multiman ult, and preferably after you've stacked Riftmaker and Conqueror. You can bait out the abilities and when they're on cooldown you can pop your ghost and run into them using ur movespeed to dodge abilities needed to get off a good ult.

Best scenarios are when you can drain stack Conq+Passive+Riftmaker on a tank before the fight and then turning on their carries to make sure the fight goes in your way and they don't 1v9 the fight.

Lillia's clear is very straight forward.

You fullclear for most of the game, as you want to avoid early fights as you're playing a scaling bruiser champ with no CC and barely any damage early on.

Start either blue or red depending on where you want to path towards and keep in mind certain junglers can tend to invade. If you're starting blue buff vs a Kindred try to setup a good ward in the river before starting your buff so she can't invade you level 2 which would end up ruining your clear.

Red buff start is the fastest for Lillia, it is about 5-7 seconds faster than blue buff start but don't let that bait you into starting it every game. Everything is situational.

Jak'sho on Lillia?
Yes, so simply Lillia's kit has always been seen as a ''mage'' where it never really fit into that category either. It has always kind of been too squishy, but not dealt enough damage either to be that

Riftmaker Lillia let's you completely 1v9 in the teamfights taking advantage of your fast kit to kite around and stack it. It is also a better bruiser mythic, and the only one for this certain build.

If you manage to stack rift, Conq and ur passive stacks you can be nearly immortal in certain scenarios if you play it right.

Let's talk about Frozen Heartand
Lillia is a very mana hungry champion and since you don't go PoM or Lost Chapter you kind of lack mana. Frozen Heart is the best armor option to purchase since it's cheap and gives you all the stats you'd want. (Armor, Mana and CDR + its only 2500 G)
For the MR opions there's only 2. Spirit Visage and Force of Nature
If they have hardcore magic damage you really need the extra mr that Force of Nature provides you with. This is a great 2nd, 3rd or even 4th item for Lillia depending on when you need the MR

Rabadon's Deathcap
This is an item which gives very little value if you build it as one of the few items, but it makes sense getting later on so when you stack all of your stuff in teamfights the increased AP it will give will be game changing for how strong you will be. It is a huge powerspike and if you manage to get to full build and have this item, your chances of winning are pretty high.

If you have any questions regarding Lillia or Hecarim
Discord.gg/Yeeter

Twitch.tv/Yeeter_1v9

Feel free to catch me live and ask in chat or join my server and send me a private message!
Thanks for reading.