When you have all your abilities (lvl 6) you can start mixing it up with enemy players. You can pick on them earlier (shoot a Baleful Strike their way), but I don't like to go in for anything serious until I have a point in "Event Horizon" and "Primordial Burst". Once you have those, when you engage hit them with "E" first, then "W", then "Q", then "R", if they are still standing, hit them with "Ignite" (which I like to have on "F" because it's right below my ulti).

E W Q R F

Later when you have "Deathfire Grasp" (which I like to put on #3) you can do

E R 3 Q R F

I like to put "Deathfire Grasp" after "Dark Matter" so I know I can get the Dark Matter to hit. Then I Deathfire straight to Baleful and then Ulti + Ignite if need be. If you've farmed enough AP with Baleful Strike then you should be really nuking it up. This build should also net you quite a few assists throughout the game especially during team fights.

This is my first build for any character so I hope you like it. Thanks for reading and feel free to comment!