Need a hand with Astra Militarum

Hi there. New Warhammer player here. We are starting to play with my group of Friends so we are adapting to all the rules and stuff (a Lot of rules and ways to play, btw). By now we are playing 500 points matches. I'm going for Astra militarum and i'm facing Necrons and Orks.

Since I only have 500 points, i'm trying to get some Leman Russ cheap version, maybe an Hydra, 1 or 2 krieg infantry, a command group and with the rest some Ogrins/Mechanicus eng/taurox.

Thats quite it. I know that My list depends a LOT on the facing player list, but I would love some advice on My construction, suggestions on the enemy armies, stratagems, etc that can help.

Also, any advice on how to move vehicles would be great.