W is statistically better at clearing, however in special circumstances, if you have a janna or good leash bot, its better to start q for clear speed, and the extra damage from Janna shield.
Level Q @ 2
Afterwards I head straight to red buff, utilizing my passive and skills and KITING BACKWARDS when both skills are on cooldown. Also use 1 potion during red buff fight.
Head to blue, and use 2nd potion. Finish blue with smite, get e. You should be around half hp+ if you got a nice leash and cleared well. At this point, depending on the enemy jungler, you can waltz to red and quite possibly get an easy firstblood. If not check both mid and top for a gank. If they are pushed, take scuttler, gromp and back. From there I buy all you can for blue smite warrior. After finishing that, rush a sighstone and merc treads. Afterwards, build towards a black cleaver and then randuins/banshees.
If you main lee sin, you need to be able to make plays. Plays such as insec the enemy carries into your team, or simply kick flash and direct it into the enemy team.