The only absolute requirement of dress code in the Kingdom is modesty. For men, this means covering everything from navel to knee. Short sleeves are therefore acceptable but not short trousers.
Anything with a waistband makes one feel unnecessarily warm in an already hot climate. Not only is local garb more practical, most Saudis take the concession to custom of wearing it as a cultural compliment. Apart from undergarments [pants, vest and skull cap], the ensemble consists of three items; thobe [body garment], ghuttera [head scarf] and aqal [head rope].
A good quality mishla [gold-edged woollen cloak] for wear at important social functions is a reasonable, though relatively expensive, investment.
Whilst the female dress code requires covering everything except the face, hands and feet in public, a woman can wear literally anything she wants providing she covers it with an abaya [standard black cloak] and headscarf when she goes out.