Need help with a team im playing

[Captain Elarix]

Ok, so im going to play this team at my friends house, it contains a tank heavy marine army, a 1100 cc nids army, a 1300 shooty eldar army and a 700 point tau army with a few kroot. And on my team its2000 point shooty marine army, a 1800 point boyz balenced ork army and a monilith necron army. and going to be played on a board with not alot of terrain, just a couple of ruin buildings. and we are playing annailation, not sure what set-up is. what would be some good tatics?

 

Thanks, Captain Elarix