your q is your mane source of damage use it to last hit if necessary but try to use e to farm caster minions. harass all the time viktor will do burst damage starting in mid game but keep them low in the beginning. if you want to be good as viktor just play him a lot and see how you would like to play him.

pros- high damage out put, good at harass
cons- squishy at beginning, hard to play

me I am pretty good as viktor I even got a pentakill 4 out of the 5 were killed by my q,
if you want to see it here it is: https://www.youtube.com/watch?v=ESr_jYDSk58