The easiest deck for grinding level 3 would be
Darkness mark
6 dragons
6 devourers
2-3 steals
2 drain lifes
and fill in to 30 cards with pillars
When you get your choice of a weapon- get a pulverizer or lobotomizer depending on future deck types you might want to build. Owls eyes are good also, but they are also the easiest to win.
or eternity, there are a lot of uses for it.
