According to this picture of Alfonso X, it seems like the standard long tunic, trews/leggings/hose. Long tunics were pretty standard for western Europe (I think even in the Roman empire too, IIRC). I'm not too familiar with that time frame, I've been reading more into Visigothic Spain lately, but most clothing styles hadn't changed too much in Europe. Makes me wonder if there were any Arabic influences on Spain in their case.