Gems and the PS4 founder pack are also available for sale. According to the FAQ,
“The Founder’s Pack unlocks all current and future gods, and also contains 400 Gems, the Exclusive Ares Soldier of War skin, and the Limited Ymir C4codemon skin, all for $29.99. It is available for a limited time to players who help test SMITE on PS4 during the alpha and beta. The Founder’s Pack will be discontinued shortly after the official PS4 launch, later this year.”
Do note that you can’t link your Xbox and PS4 accounts. PS Plus is not required.