I am just a poor soul who just found this build extremely fun and underrated to play so Im here to share the knowledge.
My elo is low so prob can't apply to high elo, still perfectly fine for casuals and for fun :D.

R + WQ: This will be your combo to oneshot squishies.

3STACKS + E + 3 STACKS + Q: not a combo but you use this to melt tanks.

Do not activate W if enemy is full HP, W scales with MISSING HP.
You cant use W once you started channeling Q.
W has no time limiter if you don't use your Q
If you channel your Q with your W activated, even if you don't use Q you will just lose your W.
W and stacks scale with enemy missing heal. Stacks consumed by Q increases in damage depending on channeling time.

YOU DEAL NO F DAMAGE IN EARLY LEVELS.
you have no item, your q deal bs damage and youre literaly useless. when you get lvl 2 get the W and start AAing and proc stacks. If they're not full(<75% hp) you can WQ and make some damage.
At lvl 6 you can coordinate with your adc and burst down adc if you hit your R.
After early game just roam and tax your midlane friend some pocket money.

You re main focus is to poke and survive till mid/late game.
On laning phase just hit charged Qs into a straigh line hitting melee and ranged minions. If enemy is in the way also punish them a little bit.
Against melee matchups poke when they try to last hit.
Against ranged just poke with Q and farm.

Your mid game starts when you get manamune, luden and booties. With these you can just roam or stay with your team and R + WQ enemies to take out a big chunk.
Don't forget to farm tho :).

When you start getting most of youre items, you can roam around and soloing squishy enemies with the ultimate combo R + WQ.
Against tanks try doing 3 stacks + E and then 3 stacks + WQ (W scales with missing health).