Despite being a card that can work in any Commander deck, typically the Sphere has been used in mono-colored or two-color Commander decks. It’s most popular in red decks, but works in any non-green deck that needs another source of mana ramp that can replace itself with a card draw when it’s no longer needed. The Sphere is also particularly good in Daretti, Scrap Savant decks and any other decks that can easily recur it after sacrificing it to draw a card.
Despite being only a common, Commander’s Sphere has become the most sought after card from the Commander 2014 decks. It’s joined by Arcane Lighthouse and Myriad Landscape as the three most popular cards from the set, and those two lands have become staples in many Commander decks. Deceptively simple cards like this are why the Commander product design teams have been able to introduce such useful staples into the format. The Landscape and Lighthouse have seen their supplies dry up in a hurry as they are useful in such a wide array of decks.
With the four-color decks of Commander 2016, it was decided to reprint it. This is great news for players who may not have wanted to pick it up as a $2 common, since it is a card high in demand and not many remain on the open market from the Commander 2014 decks. The Sphere should be a staple in four-color Commander decks going forward, as the mana fixing will even be more important than in the one and two color decks it currently sees play in.