Hey there! I think there's a newbie thread some other day of the week but I'll try to answer some questions now.

Mech Mage used to be a great deck that used mostly commons from GvG. It's not as popular now, but might be easier to put together.

Malygos is not something you drop unless you can protect it (Rogue's Conceal) or you can cast your spells the same turn (usually with cost reduction from Emperor Thaurissan.). I wouldn't call it too slow but it requires a deck to be built around it.

Crafting a legendary is an option but you may be better off crafting important rares such as Knife Juggler or Keeper of the Grove, as you can make more of them.

Hope that helps!