by Kyokai
Cadenza, Kallistar, Hikaru, Vanaah, Luc, and Magdelina are the easiest mechanically to play.Of those, Magdelina and Vanaah require a little more to pick up, despite their mechanical simplicity, they're strategically more advanced.
Khadath and Kehrolyn, conversely, are easy to play once you've picked up their mechanics, despite the levels they're grouped with. Their mechanics are a little tougher to understand, but their strategies are more obvious from when you pick up the cards.
I wish you the best of luck learning the game!