Buy enhanced cooldown. Grab spell scrolls and remember they respawn. Use feathers to walk through walls diagonally. Goblins only attack after they 'see' you by coming near to you, otherwise they follow predetermined movement patterns. This means the bottom left room is extremely crowded and vulnerable to the magic aura thingy. Fireball size increase is good, but should wait until after shadow orbs (which you can follow for safety, they are slow-moving) and several enhanced castings.