I do this for my kids when we travel. Boys either have navy or black athletic pants and shorts, and shirts that will match all the bottoms. For my girls, I love play dresses, no matching required. Or, i go with jeans and jeggings, with a mix of shirts (ls/ss) that all match a couple of sweaters and fleece jacket. I have never bought a whole set together, i just choose pieces that all coordinate. It makes packing and dressing so easy. I also find it cuts down on the number of shoes we bring.
loving my dh and our littles (dd ~ 11 yrs, ds ~ 9 yrs, ds ~ 7 yrs, dd ~ 5 yrs and baby brother ~ 20 mo)