This is a really difficult hero. There is a lots of jobs U have to do!

First: Your main job is to soak lanes for xp. U have to bodysoak a lane and soak the others with Symbiote. U can use the Toxic Nests to push the lane harder if U need.

Second: U need to be at the teamfights! ALWAYS so dont miss one! (keep, and use your Ultimate Evolution for objectives, but that means that U can't use it between them, the cooldown on it is really short.) Try to copy assassin role heroes.

It is hard to decide where to put the mines. U have 3 choices;
1.: U can make gift packs for the enemies, take 2 pack of Toxic Nest to a blindspot where they surely will move through. U also can sit on it to lure them in (but be aware! this is dangerous, they can easily remove the whole pack with a single aou spell before entering the bush, and U also may not be aware becouse of focusing on a teamfight at the same time. Keep in mind that casting the Ultimate evolution will hide your body for the duration, this also usable to survive). Only go out for ready, or half ready places, never before! Watch out that you have to keep theese Nests on! After lvl 20 you can make theese kind of surprises with Locust Nest as well.
2.: U can push lanes with them as I mentioned before.
3.: U can disturb the enemy Heroes by spreading them on the places where they move through when they switching lanes or checking bushes.
And ofc try to get there (not in person) when someone fighting with the enemy!

The Assault Strain makes U able to do a hard, fast push. But without the Survival Instincts, U have to move closer. I recommend to go out by foot and always keep one eye on the map. They WILL find U. U must be aware of that.