How can I 1v1?
The way this build works is because you build AD and AP (using devour and wits end) you can 1v1 any champ because most have more armor or more MR since you have a solid source of both you can do good damage no matter what.
What about team fights?
With this build some of the items you can build allow you to act as a support role in some cases like the Abyssal Scepter or the Frozen Heart. along with your W you help your team a lot in team fights and you can engage with your ult to maybe get a kill and shut down someone who does massive damage to your team.