Are you in a guild yet? And I do think I may be able to help ya a little. I love nightmare. He has a wonderful ability called phase. At level 5 and up, but if your talking low mana battles. I would focus on one really good tank like Groudon. Back him up with a decently healthy ranged monster followed swiftly by magic attackers. Something like the screaming banshee or to he ghost soldier dude, or the witch. Low mana cost, high magic attack. Because magic by passes the armor.

Problem is, I'm not the only one that's realized this. So you need a card that has strong defenses against magic. Like, rowster owtell. or the rusty android. Mainly, you want something like the undead lich because it heals at the same time fishing out 3 on damage per attack. (And this is level 1.) Using peak monsters to rent you can obtain a decent team for like 5 days for under a thousand dec if you shop and pay attention to what your doing. But If your doing this, definitely pick up dark ha'on. Are you building your own cards? Or renting?