Immortals should be your troops of choice. At least two strong squads of ten, buffed by lords with res orbs and if you can spare it, a cryptek with a lightning field and haywire staff. They will weather the storm of fire they take reasonably well and form an appealing target, both of which you can use to your advantage. Then you can field several additional units of necron warriors as a screen and support.
Regarding the choice of weapon, I prefer the gauss blasters simply for the AP factor. Marines aside, it's good to know most of my targets won't be getting saves from my immortals' fire. That said, there's not much negative to say about the merits of tesla either. It's up to you.
Deathmarks are also an excellent choice. I take a squad of five just to mark and damage/kill one unit that I otherwise don't want to have to deal with, typically a monster or small unit like dark reapers or command squads.
To be completely honest, it sounds atm like you're in more need of the deathmarks than the immortals but I think you should definitely be wanting both eventually.
Nonsense is our Salvation
Last edited by Serpion5; 05-25-14 at 12:14 AM.