Need warhammer 40k help?

Question

what is the best way for me to beat a necron army (no monolith) with space marines

Answer 1

This question might be better answered in the Video & Online games area.

Answer 2

Aim to take out elements of the opponent's army that are weakest against certain things. For example since flayed ones can't shoot back then destroy them with overwhelming firepower and dig into the grunts of the army with your best close combat troops. However since his grunts are probably the most numerous then aim not to completely wipe them out but fight a delaying mission, while you focus on annihilating his elements that are powerful and specilaised but few in number e.g. wraiths, flayed ones.