Honestly just farm until level 3. Your level 2 trades are not good enough unless you get a really good setup from your support. Going in too early also runs the risk of dying to an early gank, which you could avoid by saving Ambush to run away.

At level 3 you can do some small trades by going around their bot laner a little bit with Ambush (though not too far mind you, engaging from roughly the side should be fine), throwing Venom Cask and attacking up to three times with Hail of Blades. Then activate Contaminate while you disengage. Do not under any circumstance chase a kill with this build, as you are nearly incapable of finishing people off while Contaminate is on cool down. If the enemy tries to disengage do not go in further, instead just cast Contaminate and return to farming your lane. You base movespeed is not that high so it's unlikely you can even get in another basic attack when the enemy walks back, and you risk dying to a cc combo from their support.

In the early midgame you can start trying to burst people with the following combo:


use Ambush to walk into a good position, then use Venom Cask and Everfrost at the same time to root them in the poison circle. Get them to six stacks using Hail of Blades and finish them off with Contaminate. Do not chase them if they survive the combo. They can still die to Deadly Venom and you are really not capable of doing more damage beyond this. The combo for team fights is the same, except you activate Spray and Pray before Venom Cask.

The late game is where it gets fun. You no longer need to use Everfrost to keep enemies inside of Venom Cask, as the massive slow will keep them in no problem. Engage with Ambush and Venom Cask like before, except don't use Everfrost. Keep it to root enemies with dashes that get too close. Unlike before we no longer need to fully disengage after casting Contaminate.Just make sure not to get in range of any enemies and keep alternating between Venom Cask and Everfrost to keep enemies at bay whilst repeatedly activating Contaminate. If you are full build you should be perfectly capable of kiting and killing the entire enemy team this way.

Again make sure not to get too close to enemies. This includes positioning is a safe way to avoid getting flanked. It's still not necessary to chase kills as they are likely to die to Deadly Venom. If necessary you can walk forward a little bit to kill them with Contaminate, but basic attacks should not be needed - Venom Cask has a short enough cooldown to stack up Deadly Venom.