Lillia has medium early game. At this tage try not to fight untill level 5 to max your Q and get movement speed.
You can look for some poke with E to heal up back.
Also you can poke enemies with Q if possible.

In midgame you can look for some TP to other lanes and push yours. She isnt good at taking turrents, but she is so good with taking minions and jungle camps.
Try to push deeper and take all the cs and maybe look for some enemies jungle camps.
You can TP to the other lane to help in fight.

At the lategame lillia is absolute monster she deals a lot and runs really fast.
Look for some AOE passive procs to ultimate multiple people and win teamfight.
Remember you are skirmisher and not tank, so you cant take all the damage there

Lillia is medium range squishy skirmisher. She has a lot of movement speed. You should kite your enemies and not to fight face by face with them.
She has weaker early but strong late game and she can destroy frontlines really good.
In team fights you can ulti multiple people with fash. If you dont have flash you can play by frontline and deal tonns of damage. Always look for 2+ people to ult in teamfight and "control" your sleep duration

To fast cast flash with your W you can fast Flash and then W to make you closer to target.
You can use Hourglass in W and the damage still goes through.
If you need to target your E at exact position, aim your cursor on the target and missle will hit exactly this place.