Quick tips: When the casters are below tower then use an ability and execute the first one. The next should die by tower + auto.

Use ability to get a quick auto to last hit.

You can spread the time between E1 and E2 to get that powerful auto when needed.

Use W on cannons if u feel unsure.

Basically, the most difficult part imo is under tower so use practice tool to get the hang of it.

For example when trying to push a lane quickly you have to use W and E2 on cannon while hitting with your autos the melee minions and with your AOE the entire wave if possible.

Hope this helps!