In lane you are so dominant it's insane. Your tentacles offer lane pressure and can cause the enemy to attack them instead of your minions, meaning you can push very well. Your aoe and high spell damage and range for a melee champion means you can poke and push extremely well.
Try and fight as near to your tentacles as you can to ensure a strong amount of damage. If you get ganked and have ult just use it and fight underneath the tentacles, you will be surprised how quickly the enemies will die. If you don't think you can win just run if you can, if not try for at least one kill. If you don't have ult and want to fight, just get near a tentacle and smash that Q and W. In a fight if you can use Test of Spirit quickly before the enemy initiates you should, as your aoe damage from your passive and Tentacle Smash will cause you to deal much more damage.
If you have pushed the enemy under tower and you can't do much, just try poke the enemy with your Tentacle Smash or use Test of Spirit. This will mean either free damage or the enemy will initiate on you which you should win if you play it well.