Need help with playing against the AI!

If you're playing as Necropolis, Naadir is the right choice. Kill the fairies, block the archers with your primary units, and cast Plague on them with your liches – that's basically all there is to it. With this strategy, I've never lost to an Elf.

Regarding luck, only the Elf's super ability is dangerous, but it rarely comes to that. Otherwise, Banshee's Cry, Cursed Ring, Deadly Luck, and Grief on the dragons will prevent the Elf from doing anything.