There's this adorably naive 12-year-old at my FLGS who's just starting Necrons. My friend IG John and I are trying to give him a good introduction to the world of 40k. The only problem is that I play Blood Angels and IG John plays (unsurprisingly) Imperial Guard. While we can teach our friend the Necrontike all about the rules and give him generic advice like "boys before toys!" and "vehicles are really powerful in this edition" and "don't worry about it, because whatever is cool now will be lame in the next codex and vice versa, just start buy buying, painting, and building what you like," we can't give him any detailed information about Necron builds, options, and so on.
So, I come to you.
I have a few specific questions - bullet pointed below - but in general, I want to learn about Necrons, so if I don't even know enough to ask the right question, feel free to chime in with whatever you think I should know to teach the Necrontike how to crush star systems beneath his living metal boot.
Here are the specific questions:
* What are the Necron builds? As the Necrontike begins to develop interests in different versions of the Necron playstyle, how can I aim him?
* How good/bad/useful/neat are these units he has expressed interest in: Ghost Ark, Annihilation Barge, Doomsday Ark, and Necron Monolith?
* Necron Warriors vs. Necron Immortals - which is better for what roles?
Thanks in advance.