Uber-LOL - Necrons are supposed to be really uncompetitive, so you should really need tactics vs them 
But seriously, there are 2 options:
1. Assume your opponent is a n00b and doesn't know how to play Necrons = rush CC on Warriors and Phase Out in Turn 2.
2. Assume your opponent knows how to play, and then start to worry.
I prefer to plan tactics based on assumption 2, but your opponent is obviously in the first category, so don't worry about it. If you have shooty of S5+ then use that to take out the C'tan, just lots of shots should do it. But your friend is going to be really easy to Phase Out, so just go for that with an assault on turn 2. Your games should not really go beyond turn 3.
[EDIT] P.S. you realise he is using 1,014pts, that is almost a whole Necron Warrior extra. Making him drop the spare model will help you right away - 1 model closer to Phase Out.
But seriously, there are 2 options:
1. Assume your opponent is a n00b and doesn't know how to play Necrons = rush CC on Warriors and Phase Out in Turn 2.
2. Assume your opponent knows how to play, and then start to worry.
I prefer to plan tactics based on assumption 2, but your opponent is obviously in the first category, so don't worry about it. If you have shooty of S5+ then use that to take out the C'tan, just lots of shots should do it. But your friend is going to be really easy to Phase Out, so just go for that with an assault on turn 2. Your games should not really go beyond turn 3.
[EDIT] P.S. you realise he is using 1,014pts, that is almost a whole Necron Warrior extra. Making him drop the spare model will help you right away - 1 model closer to Phase Out.