Sorry, this is my first build so it's obviously rough. Vel's Q is his strongest move, you can either hit the straight skill shot on the champ or try and angle it around the minions for a slow with a gank. Remember it goes out both ways perpendicular to wherever it stops going out straight from you, and you can stop it from progressing out at any time between when you shoot it and to where the max range is just by hitting Q again. His W really helps you use his passive, if you land it on the enemy and they stay within its range when it detonates, they already have 2 counters on them, all you need to do is land another ability and there's your bonus magic damage. His E is great for team fights and stopping most champs ults by knocking them up and interrupting them. His R is also a tide turner in team fights, and for each 0.25 secs it adds a counter to the enemies it's on, not only dealing the damage from the ult but also from his passive, this is one of the main reasons I like to go build for cool down reduction.