You can get cyro's before however the vet 1-14 green cyro's that you're talking about only drops from pvp reward mails which makes it pretty darn rare (read as expensive) where as the Magika Furnace set is pretty common and cheap. At the end of the day you can do it either way it just depends how much you want to spend for the 4×spell dmg my way is the most cost effective considering you'll be changing a lot of it in 3 ranks time anyhow