Fusible interfacing for knit Playtime dress

Hi, I'm making the Playtime dress out of knit fabric but am a super novice with knits. My lightweight fusible interfacing stretches in one direction but not the other. Am I looking to preserve some stretch in the dress facing pieces (so should align the stretchy direction of the interfacing with the direction of the knit fabric with more stretch), or am I looking to remove that stretch (and align the non-stretch direction of the interfacing with the direction of the knit fabric with more stretch)? Or does it not matter? Thanks!