Necrons is a good army if you know how to balance your forces, even as you don't have many troops. Be carefull of the phase out rule as you can loose a game even if you are winning it .take in mind that the most important thing in a necron army are its troops if you can field lots of them, yo wont need to worry. Try to avoid tanks and heavy weapons as much as posible ( high strenght and low aps means you are not standing again) C'tans beautiful minis but not usefull & too expensive, besides they are like sitting ducks and every body tend to shoot at them. Their stats are good but not that good when everybody shoots at it. Try to get monolith's beautifull and every body is scared at them thei armor will hold a couple of shots, plus is great to give your troops cover and teleport.