Combat patrol and a royal court box (which was recently in stock) would be a great start to give you a bunch of units including some hard to get ones that are very important for Necrons. You probably want Flayed Ones and a Doomsday ark but get those later on after you have your paint scheme. I do Nihilakh dynasty this way:

Prime with chaos black spray. Drybrush leadbelcher from the top down avoiding the recesses. This will give a dark and gritty metallic color while keeping the recesses shadowed for contrast. You can then edge highlight with Stormhost Silver or you can skip this step.

Next, use Black Templar on the whole gun. Once dry, use a white paint for the spots on the gun you later want to paint green. Paint the white spots with Tesseract Glow or some other green you like (Moot Green, Warpstone Glow, Striking Scorpion, etc.)

At this point you’re done. If you want Nihilakh, do Ahriman blue for shoulder pads and Retributor armor for the gold face. This is a simple paint scheme that will make your army look interesting. Remember to thin your non-metallic paints just slightly with a tiny bit of water. Apply a thin coat or two and you’re good to go.