For the outlined siege build, your goal is to be a pushing champ, with the focus being on taking merc camps, and then buffing them with your merc lord talent. Seige camps should be soloable from the time they spawn, for bruiser/knight camps, wait until level 7-11+ or have some backup. Use possesion on cooldown in the lane, taking the enemies' creeps in the following order of priority: Merc (siege), Merc (CAster from bruiser camp,) Merc (knight from bruiser camp), catapault, ranged creep, melee creep.

For the outlined carry build, the end goal is to kite around enemies while nuking them down with your Q, but keep careful focus on your spacing to the enemy, you want to take advantage of your range, as you are very squishy. Prime targets are squishy melee heroes, and ranged heroes with low mobility. For example, trying to take on a tychus or raynor will leave you dead if you try to all in head on trade with them.
Poke away with your Q, whittle them down until you have the health advantage. Alternatively, if an enemy is overly aggressive, retreat with E while still staying in their range; while your E is travelling, pump all of your Q's into the enemy, press E again; Q is now refilled, proceed to throw your W to apply vulnerability and take the kill with Qs.

For teamfighting, use your R when it will do one of the following: Interrupt an important channel like a malf or lili ultimate, preemptively shut down a burst assasin, such as jaina, kale, falstad, or nova, or when the enemies are already stunned and you will hit 2+ targets