As a midlane Illaoi your goal is pretty simple. Bully your enemy mid laner away from possible XP and Gold. Maxing your Q allows your Tentacle damage to climb higher and using E regularly allows you to deal damage and spread more tentacles.

The main things to keep in mind is to make sure your at least your first two tentacles are on the tip of the walls near river. Allowing full coverage of the length of the lane. If you can push well enough put two more on the enemies too to allow for more harassment.

This isn't a typical Illaoi build or lane but I always find it fun to play it when I am bored or feel like making someone tilt.