Shogun: Date or Shiamazu are the easiest, the Date because of their starting position, the Shiamazu because of early access to the jesus and his guns. In Rise (my favorite) the Fujiwara are the easiest to play, great starting economies and positions (kill your sister clan as soon as possible) but the Taira are my favorite clan ever, challenging and regal campaign with lots of castles to fall back on in the case of set backs.