Then after crafting, you get the X/X Skeleton Horror with power/toughness equal to the power of what was crafted
Cutting a Ritual out of their deck can certainly make life harder for them, but its hardly an insurmountable problem
Inquisition of Kozilek No real shock as to the top two on this list
The best subtheme "plans" to have are, roughly in order: Crapload of spells, good card velocity (aka card draw), and Gandalf's Sanction (best) or Fiery Inscription (second best) 1 power tempt tribal
Red can easily generate mana advantage as well, be it through bursty rituals (Irencrag Feat), treasure tokens (Dockside Extortionist), free spell/polymorph effects (Fires of Invention, Tibalts Trickery), or the occasional outright mana dork/discounter/mana multiplier (Leyline Tyrant, Mana Echoes)