Necrons 500pts First List Need Help!

[Atreyu]

Hello! Long time WHFB player and since some of my friends have pushed hard enough they have gotten me into trying 40k. My first game is tomorrow with a random person I will end up against at my local GW store (I personally refuse to play my friends just yet I feel that playing against a random build of a random person I can actually think on my feet instead of basically arleady knowing what I need to kill and get ahead.) So Necrons was my pick (I play TK in Fantasy so it suits me well :D) and I drew up my first 500.

HQ
Necron Overlord-(190)
-Warscythe
-Sempiternal Weave
-Ressurection Orb
-Phase Shifter

Troops
10x Necron Warriors-(130)

5x Immortals-(85)

Heavy Support
Annihilation Barge-(90)
-Guass Cannon

Basically I throw the lord in the immortal unit and just go forward letting the barge wreck what it wants with the cannon and tesla destructor. Reason I do take the cannon instead of all tesla weaponry is because having two chances of definitely wrecking something as tough as a space marine. Though this is my first list for 40k so definitely need help!

[Dont-Be-Haten]

The 2+ armour save should be tossed to upgrade him to a Phaeron. Whatever unit he joins gains Relentless. Definitely worth it. Also, I'd stay away from the war scythe at this point level. Your units are not meant for CC. You're going to want to play move away and shoot.