Your laning phase should be pretty passive. Try to farm up with autoattacks, and trade with your Q, after it is on level 2. This build is pretty weak vs ranged champions and high burst champions, so avoid playing vs it. When you have upgraded your smtite to Skirmishes Saber, try to use the smite much for trading with your Q. You can also push the wave out with your E and then go and kill the golems/gromp with your smite. When you have your Cinderhulk and Tryforce + Boots, you can 1 v 1 nearly everyone, aslong as you kite much. Boots are very important for this type of Viktor build, due to you nearly only using autoattacks in fights. Thats why I always upgrade my Mercury Treads with the Furor Enchantment after I have my Triforce and Cinderhulk.
Viktor is good in teamfights, as long as your team is the one disengaging/kiting or chasing. Try to avoid fights where you are stacked up on one place. Your job in teamfights should be to Outkite the enemy frontline, or make good flanks on the AD/AP Carry, as long as they don´t have any peel. The Blade of the ruined King will help you while you kite their frontline, or while you chase their carries. When you have your Frozen Mallet, you can chase and kite everyone without problems. Always use your Q when you can.
Viktors Lategame is really strong with this build. You have a ton of sustain damage and your still fairly tanky. Your last item choice can be different things. I normally build either Yumus Ghostblade, Static Shiv, Wit´s End, Nashor´s Tooth, Last Whisper or Zephyr. If you need a deffensive item you can go for Guardain Angle or Banshees Veil.
Your tower pushing potential is really strong, so make use of your teleport and splitpush alot.