PROS
+ She is a beast on 1 vs 1 (I often kill before lvl 6)
+ She has huge waveclear which allow you to roam easily
+ As an exotic pic mid your oponant wont know how big your damages are

CONS
- Its a cheesy champ so if you get behind you'll have not choice to just farm peacefully (try to be the cheesiest lul)

CONQUEROR BUILD
- Conqueror now proc very easily since Lillia isnt considered as a range anymore
- Presence of Mind and Second Wind are very much needed for your laning phase for mana and HP regen
- Overgrowth has a huge sinergy with Demonic Embrace and give you some good scaling
- Always take Armor since her basic armor is so low

AERY BUILD
- AERY's damages are insane all game long especially late game
- Gathering Storm and Overgrowth give you infinite scaling and has HUGE sinergy with Demonic Embrace
- Celerity is god like on Lillia it give her legit speed hack
- Always take Armor since her basic armor is so low

Road Of Ages
It gives her so much sustain and scaling, makes her a beast mid/late

Lyandri
Always good against tanky comps, Lillia apply so much burn and pure damages you'll melt them

Zhonya
Give you such good teamfights, engage flash Q R Zohnya can make you win a game late if you sleep enough people and your team follows

Morellonomicon
Very underrated cheap Item, as an AOE champ you can apply anti heal on the whole anemy team easily

Riley
As Lillia is already so fast Rylai's will make you feel like youre spacegliding as they will be slow as snails

EARLY
LVL 1 try to last hit wave and poke your enemy with your Q
LVL 2 take W you can already take some trades with almost every matchups

Your ignite is giga broken dont hesitate to use it since it has such a low CD

try to poke while farming and if you feel cheesy you can all in LVL 6 with
E -> Q -> R -> W -> ignite -> Q this can oneshot almost every champ

MID/LATE
Lillia is a roam beast dont hesitate to fast push and roam bot
You have such a good teamfight engage with your R dont be scared to flash in Q into R
Your Zhonya is your Best friend late game use it wisely
As you have good sustain dont hesitate to deal with bruisers